OK, as of yesterday I've beaten the maingame, so I may as well give my 2 cents on the team I used. Keep in mind I was pretty underlevelled for the most part and didn't use the EXP Share, if that in any way alters how you take my judgements.
Froakie - B/C Tier
Availability: A starter, so obviously boasts optimal availability since it's the first thing you get, rofl
Stats: Immensely fast mixed attacker with a bit of a kick but not an overwhelming amount of force, which honestly diminishes the Froakie line as a whole, as a lot of the time it simply isn't powerful enough to nab the instant KOs you think it would. As a Frogadier especially, it gets into a bit of a rut in the mid-20s to the 30s due to its thoroughly mediocre offenses coupled with its poor move selection (I'll detail this lower down), but when you get Greninja (and Surf), it definitely picks up, so it's not entirely negative.
Typing: Water's pretty decent in-game all things considered, matching you up neutrally with most opponents (Dragons are rare and Grass types aren't as common as you'd assume). The Dark type granted by Greninja is really a swing and a miss though, as all it really does is allow Greninja to more safely take on the rare Psychic types and Ghosts while simultaneously granting you a weakness to the very widespread Fairy and Fighting types which further diminishes the ninja's paper defenses.
Movepool: It gets a few very good moves that allow it to excel at certain points in the story, notably a very early level 14 Water Pulse and an immensely powerful Surf on Route 12 to help make up for the relative mediocrity of Froakie and Frogadiers' offenses. However, that's all it really has going for it, as its early coverage is quite frankly atrocious, I had to make do with Round, Dig and Rock Tomb for quite some time on the occasion I couldn't simply spam Water Pulse and win, and it wasn't until fricking Dendemille when I got to relearn Night Slash and snabbed the Grass Knot TM off of Ramos that I felt remotely confident in my coverage. I managed to miss Dark Pulse in my playthrough though, and I'm sure that would've ameleriorated my problems considerably, but for the long and short of it, Froakie gets very powerful STABs at very convenient times, but there is a VERY noticeable drop off in its potential shortly following them, at least until you become Greninja.
Major Battles:
Viola: Worst matchup out of all the starters as you lack SE moves and don't resist Bug.
Grant: Good, but not as brilliant as it would initially seem, as Amaura can paralyze you and Tyrunt is hit neutrally by Water Pulse, though the AI may allow you to clean sweep.
Korina: Not ideal, as this is in Frogadier's mid life crisis where Water Pulse suddenly stops being amazingly powerful. Machoke's bulk and Hawlucha's everything are likely to beat you here.
Ramos: lol
Clemont: lo- well OK you do have Dig and (likely) Greninja at this stage so you may just be able to beat Heliolisk if you're lucky, but good luck not getting obliterated by Thunderbolt. Emolga's airborne and Magneton has Sturdy so Dig fails against them.
Valerie: Err, you can beat Mawile? You're dead weight against Sylveon and Mimey though, as you'll never break through their special bulk with Greninja and their pesky pixie powers will destroy you.
Olympia: You actually win here providing you pack Night Slash or Dark Pulse.
Team Flare: Generally performs very strongly against Team Flare thanks to its Speed and Surf hitting most of their underpowered mons for either neutral or SE damage. Manectrics are a huge pain in the knickers though.
Wulfric: You lose against Abomasnow (unless you magically got HP Fire), but the other 2 mons can be handled pretty easily depending on your moveset (Avalugg gets demolished by Special attacks, Cryogonal physical)
E4: Malva gets curbstomped and you win against 2/4 of Drasna's team, but the other 2 can beat you through their bulk and SE coverage, and Siebold and Wikstroms teams carry coverage which flatten you. The only member of Diantha's team you even have a remote chance of OHKOing is Aurorus.
AZ: lolsweep
Additional Comments: Greninja is generally great against regular trainers, but its common weaknesses, only decent strength and lack of advantageous matchups where they count render it slightly underwhelming. Missing out on Dark Pulse may have soured my retrospective on it though, and while its poor Gym matchups make me lean towards C, with Dark Pulse and strong Water STABs at convenient times, I imagine it could crack B too.
Scatterbug: - B/C Tier
Availability: First route of the game, immediately once you receive Poke Balls. No problems here.
Stats: Scatterbug and Spewpa are about as effective in battle as you'd expect a worm and a pupa to be in a frightening world of fighting-crazed dinosaurs, dragons, living weapons and mutated mammals, and so will require babying or grinding to reach its full potential, although Scatterbug learning Stun Spore does help it not be complete and utter dead weight before evolving. When you reach Level 12 though, the sleeper awakens. Vivillon's Struggle Bug is unbelievably strong when you initially get it thanks to Vivillon's amazing (for post-gym 1) stats, literally plowing through everything and 2HKOing resists like they're nothing. It inevitably falls from grace slightly once the rest of your team catches up, but even then remains just fast and strong enough to remain a reliable force thanks to its incredibly well-timed level up movepool.
Typing: Bug/Flying is unbelievably ass, especially with Fairies everywhere resisting your Bug moves, no Flying type STAB until you get Hurricane in the 50s and random Rock coverage moves slaughtering you out of nowhere, but these don't really come into play until a bit later on in the game, so Vivillon's typing isn't too atrocious early on in the game, but after Ramos is around where it starts to kick you to the curb a bit.
Movepool: Inarguably the best thing about Vivillon, its level-up movepool is incredible and ensures it strays relevant right until the end of the game. It not only gets Struggle Bug immediately upon evolving and an early Psybeam for strong effective coverage early-game, but Stun Spore allows it to support the team and help catch other mons providing you're one of those "gotta catch 'em all" players. Draining Kiss is also a godsend by giving you extra coverage against Fighting and Dragon mons in tandem with 75% recovery, ensuring Vivillon survives that little bit longer. However, like Greninja, it gets strong STABs right when it starts to slip, gaining Bug Buzz at level 35, Hurricane (which pairs brilliantly with Compoundeyes if you got that ability like me!) at level 50 and Quiver Dance at level 45, ensuring Vivillon stays relevant and up to par with the rest of your team even with the stat buffs. Set-up is a little inefficient but it REALLY helps Vivillon in the larger battles. About the only thing I'd ask for is a good Flying STAB early on like Air Cutter or something.
Major Battles:
Viola: Don't try it, Spewpa is just far too weak to try battling at this point. Grant: Have you ever seen a butterfly win a fight against a boulder before? Don't try this unless you're suicidal.
Korrina Even with your 4X resistance, Machoke's Rock Tomb ensures you won't sweep this gym and Hawlucha's Flying Type will wreck you.
Ramos: Disregarding Jumpluff's Acrobatics, you do pretty well here.
Clemont: You'll be fried before you can say "Bug Buzz".
Valerie: Fairy resisting Bug means you've not got much business here either unfortunately.
Olympia: You only actually win against Meowstic, Sigilyph flies and Slowking for some reason has Power Gem, pretty much emblemising my comment on random Rock coverage moves.
Team Flare: Whilst OHKOing Toxicroaks and Scraftys will never stop being hilarious, the likes of Houndoom, Swalot and Manectric are all a pain in Vivillons' side.
Wulfric:You win against Abomasnow and possibly Avalugg if you're lucky, but Cryogonal will triumph literally 100% of the time unfortunately.
Elite 4: None of these are positive matchups for Vivillon. You could TRY and set up against Siebold's Clawitzer, but somehow I doubt it'd work out too well, and the rest either wall you, outright murder you, or do both consecutively.
AZ: Terrible
Additional Comments: Similarly to Froakie, what would otherwise be a fantastic mon gets marred slightly by poor Gym matchups and common weaknesses, although it's safe to say Vivillon is one of the best ingame Bugs this side of HG/SS Scyther and I urge more people to try it out. It's not bad people, it actually kicks ass! Definitely leaning more towards B, but getting screwed over by Rock moves and its stats letting me down very late in the game makes me open to a high C too.
Skiddo: - B Tier
Availability: Comes shortly after the 1st Gym, and is relatively common in Route 5 too.
Stats: Incredibly well-balanced and equally distributed, none of Skiddo or Gogoat's stats go to waste, and it showed in its in-game performance, as it was hands down the most consistent member of my team, solid bulk coupling with high attack and relatively decent Speed to make a reliable Pokemon that could take on almost any situation and come out triumphant (and if not, having made its mark).
Typing: Pure Grass is rather poor offensively but isn't bad defensively, taking many hits neutrally and taking SE hits easily thanks to its brilliant bulk.
Movepool: While early on Skiddo's movepool seems atrocious outside of consistent Grass STAB, purchasing the Bulldoze TM in Lumiose City grants it some really nice early-game coverage in Grass+Ground, and it also learns Take Down relatively soon after if you're feeling really ballsy and want to take on Fliers and Bugs with Skiddo and not another mon. Leech Seed is a fantastic move on a mon as bulky as Gogoat, and ensured even in battles where Goat wouldn't win, it would contribute towards an eventual victory and help preserve either itself and/or the other members of the team, although it becomes redundant somewhat when you learn Horn Leech. Although Gogoat's offensive movepool is limited (it gets Brick Break and Aerial Ace, but not much else), it can be a great HM slave, learning Strength, Surf and Rock Smash (the 2nd of which can also be a good general move too) for convenient playthroughs.
Major Battles:
Grant: Amaura kinda destroys you and Tyrunt is neutral to Grass, not too great.
Korrina: Can beat Mienfoo and Machoke no sweat, but Hawlucha is scary.
Ramos: No reason to use it here at all, even a Gogoat mirror fails as it has Sap Sipper.
Clemont: Emolga's a bit of an ass, but Magneton and Heliolisk can easily be taken down with Bulldoze. Gogoat does a fine job here.
Valerie: Does well against Mr. Mime and decently against Sylveon, can Bulldoze Mawile too but isn't an optimal choice.
Olympia: Slowking gets destroyed, Sigilyph beats you unfortunately though.
Team Flare: Bulldoze and sheer bulk go a long way in granting Gogoat a surprisingly decent matchup against a lot of Team Flare, though Fire Types and Swalot/Croagunk are best left to other members unless you want to heal after every battle.
Wulfric: NO.
Elite 4: Siebold gets torn apart (aside from Gyarados) and Bulldoze/Brick Break/Earthquake deals with Wikstrom decently (aside from Scizor), Malva and Drasna are best left to other members though, as is Diantha.
AZ: Beats Golurk, loses to the other 2.
Additional Comments: Not a lot else to say, it was my most consistent member by far, pulling through when I needed it to and in a lot of situations I wouldn't expect it to as well, supporting the team and pulling its weight all the while. Horn Leech and Leech Seed also made it the member least reliant on potions for healing, which is always a plus!
Amaura: - D Tier
Availability: Between the 1st and 2nd gyms, although it comes with an opportunity cost of not being able to pick Tyrunt.
Stats: Amaura is slow but surprisingly powerful and rather tanky and durable, a combination which unfortunately is at odds with that atrocious typing, rendering it easily hit for SE damage and oftentimes its bulk is compromised by its numerous weaknesses, making it seem a lot less bulky than it really is. However, it's powerful right out of the box, with powerful attacks and a great ability which buffs moves like Return and Take Down significantly, giving you pseudo-STAB and helping dent things (or take them out) very effectively.
Typing: Oh my GOD I am never ever using Amaura in-game again, and predictably, this is the sole reason as to why. Seriously Ice/Rock is a really cool typing, but in-game it is beyond a joke, with Fighting types being amazingly common and Steel coverage moves literally revealing themselves out of bumfuck nowhere. You could be facing a Pidgeotto or a Shelgon or something you should theoretically tank and effortlessly KO, but NOPE, they use Iron Head, Flash Cannon, Steel Wing or whatever and you suddenly have a fainted Amaura/Aurorus, it was the most proposterous farce you could imagine and made even battles you were confident you could win into a guessing game of "does it have a Fighting/Steel coverage move or not" that really put down Amaura's performance and made using it a total chore. On the plus side, Ice and Rock is a great offensive combination that kills a lot of stuff, and Aurorus certainly isn't lacking in mixed firepower.
Movepool: Aurorus' movepool is a little mediocre, but it has everything it needs to be a strong contender. Refrigerate turning your Normal moves into Super-STABs, Bulldoze to help hit Steel mons, Freeze Dry to act as insurance against Water Types as well Thunderbolt for additional coverage and Rock Tomb for near immediate Rock STAB that also helps alleviate its poor Speed. A pretty strong movepool, not particularly large, but certainly enough to get the job done.
Major Battles:
Grant: Rock is SE on Ice and both Amaura and Tyrunt can hit with Rock Attacks you lack.
Korrina: Are you mentally challenged?
Ramos: Unusually, although it's weak to Grass, Amaura has the bulk to live a few attacks and can use this gym as quite a good training spot! Gotta have lots of potions though, which isn't exactly the best plan of action, but Amaura can do work here!
Clemont: Bulldoze can do work against a lot of Electric mons in here, but watch out for the Magnets, their Steel moves will obliterate you without remorse.
Valerie: Refrigerate Return deals good damage against a lot of the mons in this Gym, but Mawile and Klefki are huge threats and Aurorus' low speed makes it a fairly subpar choice to sweep through the gym.
Olympia: It's just too slow.
Team Flare: Deals with the Bats VERY nicely (minus Xerosic's Crobat, goddamn Steel Wing X..X) and Bulldoze beats Fires/Electrics/Poisons. A good grunt killer, but again, needs continual healing to stay healthy.
Wulfric: Rock Tomb helps you beat Cryogonal, but I wouldn't recommend Aurorus here.
Elite 4: Malva's Talonflame gets beaten by Rock Tomb, and Drasna gets swept dry aside from Noivern's Focus Blast, but nothing else matches up well for Aurorus (Freeze Dry failed to OHKO Gyarados X.X). Beats Diantha's Gourgeist (and Goodra thanks to Focus Miss ^.^) though.
AZ: Golurk and Sigilyph are beaten, Torkoal is best left to something else.
Additional Comments: While I sound immensely negative and honestly never want to use this thing again for as long as I live, Amaura has a lot of positives buried within its laundry list of shortcomings, making it perfect D Tier material. Use it carefully and make the most of its unique traits and it should be a pretty strong member of your team. Tyrunt is probably more consistent and a LOT less stressful to use though.
Klefki: - C/D Tier
Availability: Very late, comes after Valerie and the hope Poke Ball Factory fiasco, so rather poor availability that renders it as a difficult fit on one's team.
Stats: Like Gogoat, nothing goes to waste here at all, a very balanced set of stats that allow it to just about deal enough damage to be viable and just enough bulk to be a reliable pivot. Mine was Relaxed, but still accomplished everything it needed to do and was probably the team member who fainted the least. Being in the Fast EXP group, immediately gaining Dazzling Gleam by virtue of coming after Valerie and the route it's on being littered with Dark types additionally made training it very easy, and it was on par with the rest of my teams' levels practically all the time.
Typing: Amazing. Steel/Fairy grants 2 very useful immunities while simultaneously dealing with the influx of Fighters and Fairies and garnering only 2 relatively uncommon weaknesses. I chose Klefki pretty much solely because of this factor, and it lived up to its incredible typing by taking down anything it needed to. Strong neutral hits such as High Jump Kicks from Hawlucha and Mienshao were a problem though, as Klefki's only mediocre bulk made it ineffective as a catch-all behemoth and much more of an insurance mon against Fighters, Fairies and Dragons which threatened me, a niche which it accomplished incredibly well but additionally meant it was the member I used the least overall.
Movepool: Shallow, but Play Rough and Dazzling Gleam gave me strong STAB on both sides of the spectrum, Foul Play gave it options against Ghosts and Psychic types, and Mirror Shot was my move of choice on Fairies. This was literally the set I used on it throughout my time with it, and while not particularly great, it accomplished everything it needed to. Including OHKOing Aegislash with Foul Play.
Major Battles:
Olympia: Resists Psychic but can't quite do anything of significance back as Psychics tend to lack Attack to use with Foul Play.
Team Flare: Scraggys and Scraftys are dealt with handily, but Klefki doesn't match up too well against the other mons they use.
Wulfric: While Mirror Shot is a pretty weak STAB, it deals with all 3 of Wulfrics mons pretty easily!
Elite 4: Laughs in Drasna's face and takes down Diantha's Hawlucha and Aurorus reather handily, but isn't too great otherwise.
AZ: Yeaaah I'd rather not
Additional Comments: I used it expecting it to be on Smeargle/Wobbuffet levels of uselessness, but Klefki defied all the odds and proved to be an immensely solid member of my team, even though I only really brought it out when I was up against something the rest of my team couldn't handle. It's very difficult to justify using so late in the game, especially if you already have the Steel or Fairy base covered, and won't be sweeping through absolutely everything like a Lucario, Sawk or a Charizard Y, but providing you invest in training it a little bit and playing to its strengths, it will surprise you. This thing is definitely NOT useless ingame.
Noibat: - D/E Tier
Availability: Amongst the worst in the game. It's after the 7th Gym, in an optional cave, only appears in ceiling drop encounters (which can be SRed for but are really hard to notice initially) and is rare in those encounters to begin with. So yeah, you REALLY have to go out of your way to find one of these, although being able to SR for a beneficial natured one might help.
Stats: Noibat's stats transcend "laughable" and ascend towards some form of bizarro futility which even Magikarp can't achieve. For crying out loud, my neutral natured Noibat couldn't even 2HKO a Gurrdurr of the same level with Fly! However, being at Level 45 means you don't have to contend with this atrocity for long (I had 2 Rare Candies so only 1 level of torture for me), and... while Noivern IS substantially better than Noibat, it's also weaker than Greninja, who already had minor strength issues of its own, so I was actually pretty underwhelmed with Noivern's power, even after relearning multiple fitting attacks with Heart Scales. It's very fast though, and generally always 2HKOed what it was up against, for better or for worse (worse imo since it should be OHKOing most of the time)
Typing: Worse than you'd expect. Being a Dragon is quite detrimental for Noivern, with so many trainers using Fairy types and all, and the random Rock coverage moves used by random trainers often left a dent in it that required continual healing. Its Flying type was pretty useful, but was let down somewhat by only mediocre Special Attack.
Movepool: Very diverse and learns a lot of powerful moves, including Hurricane, Super Fang, Boomburst, Focus Blast, Flamethrower, Shadow Ball and Dragon Pulse. However, all of these are reliant either on TM purchases or on Heart Scales, and the nerf in the power of some of these moves combined with Noivern's already underwhelming stats made a lot of its moves fairly inconsequential as very rarely would the move in question OHKO. Don't even bother with Air Slash, it's FAR too weak and I regret not replacing it immediately with Hurricane when I had the chance.
Major Battles:
Wulfric: Don't. It can beat Abomasnow with Hurricane but you get OHKOed by everything.
Elite 4: Surprisingly ineffectual against Drasna as all of her Dragons have some degree of bulk that allow them to live a Dragon move, and her Noivern will likely outlevel and outspeed yours. Does OK against Siebold and Malva I guess, but does nothing of worth against Wikstrom.
AZ: Not a lot here either
Additional Comments: As sad as I am to say this, Noivern severely let me down. Whether it was due to shit IVs, redundancy with Vivillon as a Flying type and most of my team as Special Attackers, middling attack power or over reliance on outside help for its only worthwhile moves, I wouldn't recommend Noivern at all unless you're a really really big fan, as it was generally an underachiever and by far the most expendable member of my team. Not recommended, I'd push for E personally, but I may have just had a really shitty draw with IVs, so a low D I'll also accept. And this is totally ignoring the complete and utter farce that is Noibat as well as the effort needed to find it in the first place.
Apologies if these opinions are subpar, but I'm just giving my 2 cents of how they performed in this specific playthrough, and thought the extra opinions on some mons (particularly Klefki and Noibat) would be rather helpful. I'll further justify my choices if anybody needs an explanation.
