Don't compare Greninja to Weavile please. Greninja has STAB on every move it uses thanks to Protean and therefore it hits much stronger than Weavile can. In addition, it has a massive moverpool that Weavile dreams to have that allows Greninja to bypass the major part of its checks, they are just different mons, and the fact that they are both extremely fast and frail doesn't mean they are mons on the same level. Regarding the comparison with Bisharp and Tyranitar, they are just much better than Weavile lol because they are much reliable than Weavile and I don't see how they lose to the Lati Twins tbh since even EQ / HP Fire fails to OHKO Bisharp and they aren't too much common anyway. In addition, Weavile doesn't 100% beat Lati Twins as well, since if they don't switch out and you use Pursuit, they can tank the hit and they OHKO back Weavile.
In the Salamence era it was a bit better than now I guess, I know it failed to know bulkier Salamences but it was one of the few mons that could revenge-kill it once it was a bit already weakened, but that doesnt matter much since Salamence is banned.
Also I know that using Lopunny, Beedrill and Sceptile takes up your mega slot (even if regarding Lopunny I wouldn't call it a waste since it's probably a top3 mega as of now), but it was just to make an example that in the current metagame there are mons that are faster than Weavile even without using Choice Scarf / boosting their speed in any way, so there are mons that can act as revenge-killer like Weavile can do.
I agree that Weavile has its niches, but it isn't as good as some people describes it imo. I wouldn't put it above B rank tbh.
PS: if Greninja gets banned, how Weavile will get better? most likely it will get worse since as of now it's one of the few mons that can outspeed and revenge-kill Greninja and thats a good niche.
idk, i'm comparing weav to greninja since theoretically weavile can run a knock off/icicle crash/low kick/poison jab set, just like greninja's best set is gunk shot/low kick/ice beam/dark pulse. they have the exact same coverage. while weavile has a stronger dark-type (and knock off, no less) and ice-type attack, gren has a much stronger poison-type move in gunk shot (120 + stab) and a slightly stronger low kick, especially if it runs 92 atk EVs. both are very susceptible to priority (aqua jet, bullet/mach punch, brave bird), but weav also has an unfortunate sr weakness, meaning that it needs rapid spin/defog support (if running this set). you're right about the movepool part, but i'd like to mention that you can use aerial ace > poison jab if you really hate keldeo and mega hera, since it 2HKOes both of them.
even then, however, weavile's poison jab, while much weaker than greninja's mighty gunk shot, still has its uses:
252 Atk Life Orb Weavile Poison Jab vs. 0 HP / 24 Def Mega Gardevoir: 294-348 (106.1 - 125.6%) -- guaranteed OHKO
252 Atk Life Orb Weavile Poison Jab vs. 252 HP / 252+ Def Unaware Clefable: 190-224 (48.2 - 56.8%) -- guaranteed 2HKO after Stealth Rock and Leftovers recovery (clef can't ohko back without SR)
252 Atk Life Orb Weavile Poison Jab vs. 16 HP / 0 Def Azumarill: 260-307 (75.3 - 88.9%) -- guaranteed 2HKO (while it doesn't ohko, this move can catch any azu arrogant enough to try and switch into weavile, especially after one or two rounds of SR damage)
meanwhile, if the team running weavile finds itself weak to keldeo and mega hera...
252 Atk Life Orb Weavile Aerial Ace vs. 0 HP / 0 Def Keldeo: 177-211 (54.7 - 65.3%) -- guaranteed 2HKO (and considering this thing's a very common switch in to weav...)
252 Atk Life Orb Weavile Aerial Ace vs. 40 HP / 0 Def Mega Heracross: 291-343 (93.5 - 110.2%) -- guaranteed OHKO after Stealth Rock
will weavile be on the same level as greninja? no way. but i'm just pointing out that this thing can beat up offense really well if played correctly.
Greninja and Weavile are completely different mons. Weavile wishes it had a move like Gunk Shot and it also simply doesn't have the coverage Greninja has. Greninja also gets STAB behind every single move thanks to an actually useful ability, making it hit way harder. And rocks do hinder it, as these calcs show:
252+ Atk Life Orb Adaptability Crawdaunt Aqua Jet vs. 0 HP / 24 Def Weavile: 161-192 (57.2 - 68.3%)
252+ Atk Choice Band Huge Power Azumarill Aqua Jet vs. 0 HP / 24 Def Weavile: 163-193 (58 - 68.6%)
^good chance to die after rocks + 1 lo round, and guaranteed after 2 lo rounds.
252 Atk Talonflame Brave Bird vs. 0 HP / 24 Def Weavile: 195-231 (69.3 - 82.2%) -- 56.3% chance to OHKO after Stealth Rock
^jolly Talonflame, Adamant is guaranteed with rocks, although none OHKO at 100%
252+ Atk Choice Band Dragonite Extreme Speed vs. 0 HP / 24 Def Weavile: 201-237 (71.5 - 84.3%) -- 68.8% chance to OHKO after Stealth Rock
So yeah SR does make a difference. Yeah sure every team runs Defog / Spin but its not a good thing that you have to make sure SR is not up for Weavile, because that could mean defogging your own hazards, which is bad for Weavile as well. Sure Bisharp and TTar both fail to outspeed but ScarfTar is pretty much outclassing Weavile in terms of pursuit trapping Latis. Bisharp also has priority to force mindgames, but each time you bring Weavile in you have to pray he doesn't use Draco. Coverage doesn't really matter for Weavile, because first of all Poison Jab is simply unviable, and secondly all the coverage doesn't matter if you can't OHKO stuff you hit SE not to mention a ton of mons that resist and are hit neutrally. Your last sentence really hit the point and sums up Weavile. It outspeeds a lot, but can't KO the targets it wants to.
252 Atk Life Orb Weavile Icicle Crash vs. 252 HP / 252+ Def Chesnaught: 218-257 (57.3 - 67.6%)
252 Atk Life Orb Weavile Knock Off (97.5 BP) vs. 252 HP / 252+ Def Slowbro: 265-312 (67.2 - 79.1%)
252 Atk Life Orb Weavile Icicle Crash vs. 252 HP / 252+ Def Amoonguss: 307-367 (71 - 84.9%)
252 Atk Life Orb Weavile Low Kick (80 BP) vs. 252 HP / 0 Def Empoleon: 239-283 (64.2 - 76%)
and speaking of Greninja wannabees lol
252 Atk Life Orb Weavile Low Kick (60 BP) vs. 4 HP / 0 Def Greninja: 224-265 (78.3 - 92.6%)
there's a lot of problems with this post. firstly, while it lacks gunk shot, poison jab is still enough to get the job done against mega gardy and azu (with some prior damage in azu's case). also nice to see that talon calc, most of them run adamant CB, which OHKOes regardless of SR or EVs. espeed still isn't guaranteed to OHKO meaning weav can take it down while sacrificing itself. poison jab unviable? hell no, it's even listed on the analysis page. how does scarftar outclass weavile in terms of pursuit trapping lol... it's not like scarftar likes draco meteor either, especially with SR on its side, and its pursuit fails to OHKO lati@s either, if they decide to stay in!
and btw wtf is slowbro going to do back? hope for a lucky burn? flamethrower (better than fire blast imo) fails to ohko even with SR, and if it tries to abuse regen, weavile can use pursuit. if sleep clause's active, amoonguss completely fails. empoleon once again needs to rely on a lucky burn (flash cannon's very rare), although it can phaze too. as for greninja, i think weavile would rather use knock off if it really needs to, as a non-LO gren becomes waaaay less threatening.
Anyways about setup fodder Weavile could also easily become setup fodder for like stuff that can force it out as well. A ton of stuff can force it out and then start setting up.
i'd like to mention that it's not THAT easy to set up on weav, especially if the wannabe greninja set actually becomes popular. yes some megas can force it out (scizor, intimidate gyara and even then low kick, lopunny, beedrill) as well as some pokes which don't really care about knock off (such as azu and clef), but it's not like scarfed things where if you get locked into the wrong move you get screwed, since not very many things resist ice+dark stab, especially when backed by nasty effects. speaking of nasty effects, i'm surprised nobody mentioned icicle crash's 30% flinch rate, combined with weav's insane 125 speed. yes it's very unreliable, but can come in handy at times.
now watch as gamefreak gives it serene grace in gen VII