Hello! I figured I'd give my 2 cents on the mons being discussed and then make a nomination of my own!
Regidrago: C- to
Unranked
As far as I'm concerned, this thing absolutely should be unranked; I fully
agree. I won't beat it down any more than it already has been, but I genuinely see no niche that it has in the metagame versus any other Dragon-type, especially because it is so readily stone walled by literally any Fairy-type (which is a borderline necessity to have in this metagame). Even when these counters have been removed or mitigated, Regidrago's breaking power leaves much to be desired, also folding to a majority of Special walls and the wide array of Steel-types to bat. When things like Garchomp, Hydreigon, and Dragapult exist in the metagame and are able to provide actual utility to teams in need of progress or consistent wallbreaking, Regidrago as a Dragon-type looks and is beyond underwhelming. Don't use Regidrago unless you're trying to be funny, which it isn't even that good at being anyway.
Heatran: A+ to
S
I
disagree with this. I feel the Pokemon that constitute being an S tier are mostly defined through polarity, consistency, and a general lack of competition. While Heatran is a very consistent Pokemon very deserving of its rank, I can't see it getting any higher than this, simply because using Heatran has an opportunity cost against using something like Ferrothorn as a Spikes setter, since it compounds common Steel-type weaknesses and limits potential team slots to cover other bases. In other words, it competes with other Steel-types pretty constantly for a team slot, which I think does need to be considered. Additionally, I feel it also lacks that S tier "you-can't-go-wrong-with-this" kick that you get with Urshifu and Magearna, which only further grounds and highlights its proneness to be competed with for that Steel-type/Stealth Rocker slot. Although it is an extremely good Pokemon with a great niche in the metagame, I can't really see it in S tier.
Moltres: A- to
B+ or B
Definitely
agree with this. Although it certainly has some pretty one-of-a-kind defensive application on teams in need of a good Fighting- and Steel-type resistance while also having STAB Flamethrower and Scorching Sands, it simply just does not perform as well as it used to for three reasons: metagame adaptation, competition, and Pheromosa. For starters, Knock Off spam has become incredibly prevalent in the tier, and given how reliant Moltres is on Heavy-Duty Boots, this is a severe problem for its role as a Defog user, and is worsened by the fact that it only allows Moltres to come in on Ferrothorn once only to get its HDB knocked off and lose its ability to not only consistently remove hazards, but also lose its otherwise awesome defensive application on teams. Things it should check in theory can also 1v1 it even so, with Melmetal adapting with the use of Rock Slide and Cinderace winning 1v1 with Gunk Shot poison. Secondly, it has extremely stark competition with Hydreigon, Mandibuzz, Tornadus-T, and Zapdos as a Defog user, as all more consistently deal with what they're meant to deal with (with Hydreigon beating Heatran and Zapdos beating Ferrothorn with Heat Wave as well), all while not being crippled by Knock Off. Lastly, being in theory the best Pheromosa answer means nothing when Pheromosa isn't even in the tier. I feel its proneness to metagame adaptation and competition, though, are its biggest problems, and I think its ranking should reflect that.
Porygon2: C- to
Unranked
100%
disagree. Porygon2 has a niche in Teleport + Trick Room similar to Slowbro, but also compresses a Spectrier answer for Trick Room teams, which I think is absolutely vital given how easily Spectrier bodies the archetype otherwise. It also pairs really well with the Slowtwins defensively. I will not disagree that Porygon2 is definitely a niche pick (in part to the fact that Trick Room is a gimmick), but I think it is a pretty strong, defined setter in the TR archetype in current stage OU and I cannot see this thing dropping for that reason.
Latios: B+ to
B
Absolute
disagree; if anything, I feel it deserves to rise again, but I'll save my thoughts on that for later. Latios may experience pretty troubling 4MSS, wanting to cover several bases at once, but its Specs/LO sets sting like all hell and it has the coverage to take advantage of its power. From my experience, Psychic-type STAB, Mystical Fire, and Aura Sphere are really good for covering as many bases as possible on their own, and it even has Draco Meteor for a good nuking option. Even outside of this, Latios can viably run options like Surf and Ice Beam to mix and match its matchups. What's not mentioned really either is that it does have options and pretty helpful resistances, such as Trick on Choiced variants, Calm Mind, recovery, and awesome resistances in Fighting, Grass, and Fire with an immunity to Ground. I feel Latios is in a bit of a tricky position because of 4MSS, but I think it has a lot of potential to become a strong option in the metagame and lowering it to B where mediocrity begins to become more prevalent does not click with me.
Blaziken: B+ to
B
I sadly
agree. Blaziken went from an Ubers worthy menace to a really inconsistent, kamikaze hot wing. As a Speed Boost user it's in a really awkward speed tier where it is forced between both Adamant and Jolly, and consequently it is forced to toss up Swords Dance and Protect for either explosive strength or a consistent speed boost. If it uses both, it loses a vital coverage option and autoloses the Toxapex, Latios, Dragapult, Tapu Fini, and Slowbro matchups. If it uses Earthquake/Knock Off/Thunder Punch, the Blaziken user is forced between Swords Dance/Protect, and still has to sacrifice consistency in some matchups anyway. I've found some success on dual screens, but even then it dies pretty quickly due to Life Orb and Flare Blitz recoil. Blaziken is just in a really sad state right now, and I think it's going to be really reliant on metagame trends or a major tech breakthrough if it wants to see success in the tier again.
Zeraora: C+ to
B-
I actually do
agree with this, but I think there is one detail that was missed in the original submission and that's how good it is at spreading Toxic and Knock Off removals. Its speed tier and operation as a pivot is definitely a point in its favor, but the fact that it can threaten its best switch-ins like Hippowdon, Landorus-T, and Garchomp with dangerous item removals and crippling status does actually help teams quite a bit, and STAB Plasma Fists/Volt Switch is a cool way to pressure or play around a majority of that may be ok with switching into a Knock Off or a Toxic such as Corviknight and Tapu Fini or Amoonguss/Tangrowth/Heatran for Volt Switch. I still think it's really niche because it can be pretty underwhelming and even debilitating otherwise in its new matchups, but it does have some pretty cool points in its favor worth mentioning.
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And now, here's my own nomination (and it's not niche I swear-):
Melmetal: A+ to A
Although Melmetal is incredibly strong with a Choice Band set and a pretty cool offensive AV user, as a Steel-type it faces a lot of competition from other options like Magearna, Excadrill, Ferrothorn, and Heatran that are either polarizing (in Magearna's case) or compress utility for teams. As far as what it brings to the table, Melmetal being as slow as it is for an offensive Pokemon alongside the prevalence of contact recoil moves makes it very prone to being chipped down throughout the course of the game, and even with this it has a lot of natural defensive answers in the tier, such as Zapdos, Landorus-Therian, Slowbro, Hippowdon, Corviknight, Moltres, and Toxapex that either press it for coverage or give it a difficult time in actually finding the ability to break holes into the opposition. Even adaptations such as coverage options or Protective Pads, I feel, are meaningless, as it means Melmetal is forced to give up the power of a Choice Band or the special bulk given through an AV simply to not be pressured by the aforementioned variables. Fundamentally, I don't think it really works as well in this metagame as it should, since it has so many natural checks and is inevitably going to be chipped down severely and lose value as it loses HP, and it faces a wealth of competition with other Steel-type Pokemon that perform in their roles more consistently. There's a reason it's dropped in use lately, I feel, and I think its ranking should reflect that.