- What overcentralization for Aegislash is so required anyway? It's no sheer ridicolous Mega Kangaskhan/Mega Gengar; It's no extra 20 Speed, massive Def/Atk output boost Mega Salamence (I called that ban when I saw its new speed, tho speed might sound pointless to some), it's no SuperFast-MassOHKO-AllSTAB-arChansey-Greninja; it's no 80 BP Priority backed by 105+Huge Power Mega Mawile (altough on that one, well, I lack enough data to comment in its defense, so no comment); it can run a plethora of sets, cool. so what? Is it the only one versatile Pokèmon? Landorus-T, Latios, Landorus-I, Mega Charizard Y (who can do more than just spam FireBlast/Flamethrower/Use Dpulse,SolarBeam, FocusBlast as coverage or Roost and the D-Dance I've seen for the sake of ... wasting a slot and letting an "idiot" wonder if it's using CharizarditeX) Talonflame, Rotom-W, BRELOOM (who someone blatantly (or stupidly) mentioned it DROPPING IN USAGE if Aegislash is ever to return), list might go on; not to mention, its so called "versatility" still has it leaning towards 1-2 sets, at best; while the rest gets outclassed; so, what "exactly" is it kept even banned for or question in its ban for? All I have read are melodramatics "the epithome of ridicolousness and overcentalizing 50-50 cents and whatnot".
None of the Pokemon you listed are near as versatile as Aegislash. Aegislash can run offensive and defensive sets, having insane bulk and good or great offensive output no matter the set. Landorus-T can run Scarf, SD (Salac or Double Dance), or SR. SR Land-T isn't even good anymore, with the rise of things like Lopunny it gets competition vs Hippowdon, which is better in most cases. Latios has niche sets like Memento, but besides that it can only Defog and Calm Mind, not really that versatile. Lando-I will either be RP, SR, or 4 Atks, there isnt another set that's seen often. Charizard Y has no versatility, Dragon Pulse is terrible on it and Dragon Dance is a joke of a set. Charizard Y literally only has one set, and it's Fire Blast/Flamethrower | Solarbeam | Focus Blast | Roost. Talonflame can go offensive, stallbreaking, or bulky SD, so it's decently versatile. Rotom-W lol. It only has one good set that isn't niche, and that's the standard one. Breloom isn't even good without Aegislash.
Aegislash has so many sets, they don't "outclass" other sets, it depends upon what you want to do with Aegislash and what kind of team you're running / you want to run. Aegislash can run the standard leftovers three attacks, spell tag three attacks, air balloon 4 atks, pursuit, balloon w/ pursuit, life orb, subtoxic, sub two attacks, and lo sd. All are viable and none of them "outclass" another. Unless you're playing full stall or hyper offense it's insanely hard to accurately guess what kind of set a competent player will be running.
You mention overcentralization but didn't explain why you don't think it's overcentralizing. Aegislash had 52.7% usage in the live suspect tours and a 48.3% win percentage. Everyone knew Aegislash was going to be brought and it still managed to win nearly half of its games, and this includes Aegislash vs Aegislash games.
- It's SLOW (and I mean, SLOW) AND its tanking capabilities only take it thus far and not as far as to even require an EQuake, Earth Power, Ghost, Dark, Fire Attack to wear it down; strong neutral attacks will STILL dent its so good "non recovery tanking capabilities" (Water Attacks from that "disgusting Pony Unicorn I mean Keldeo", tho still what you call an "S rank", but even "non S Ranks", like Gyarados, not to mention the already existing plethora of attackers which already used to pack attacks which also happen to put a huge dent on Aegislash like Knock Off Scizor, Azumarill (which is also slower than Aegislash and can hit it in Blade form AFTER TAKING A HIT), anything out of the 20+ Pokemon that can learn it ("oh noes, king shield"), VENUSAUR (a beast which might also require some specific team building, else you'll have a not so easy time beating down a "Tank" or "Wall" which actually packs some decent recovery and solid attacks, tho can still get worn down), the "dropping" BRELOOM (who can just put it to sleep and call it a day, similar to Venusaur, tho not necessarely), and I might just go on; my point is, I don't understand this overcentralization at all; as "someone" said, "checks suffice; and I can count more than Landorus-I's or Charizard-Y's, to be fair.
Aegislash has crazy bulk, it may be possible to "wear it down" but it's not near as easy as you make it out to be, and if you're switching Aegislash into a Keldeo or your opponent is someone is making some pretty bad plays. Aegislash isn't a 'Mon that is going to beat every single 'Mon, it's one that's insanely strong and bulky that beats over half of the metagame by itself. Idk why people keep mentioning Gyarados as an answer to Aegislash. One of these will happen;
A) You're switching it into a Shadow Ball / forcing a 50/50 on switching vs attacking on the King's Shield / Attack, and if you lose your Gyarados will lose 50% of its health.
B) You'll give Gyarados a free switch, whether by U-Turning on the switch in with something like Jirachi or Celebi, saccing a 'Mon to Aegislash, or making a double switch. Only one of these is a smart move and that's u-turning, which isn't something you'll be able to do everytime and is definitely not going to be reliable. Double switching is perfectly fine if you're capable to pull it off, but the risk vs reward shows it's very rarely worth actually pulling it off, especially with a 'Mon like Gyarados, which will most likely be your primary win condition. Not saying it can't be done, but it's a very risky move and not something you should have to rely on vs what would be the most common 'Mon. If you have to sac something to Aegislash to bring in a Mon, you probably can find a better answer or just maybe this 'Mon is broken.
Things like Scizor, Azumarill, and Venusaur are obviously things that Aegislash shouldn't be staying in on, but none of them can safely switch in and consistently. All three lost straight up to fast LO Aegislash (Shadow Ball and Iron Head 2HKO all three), Spell Tag 2HKOs Venu and Scizor, and it's just insanely easily to wear down Azumarill to the point it can't check Aegislash / another 'Mon it would need to check anymore. None of those are legit answers nor are they safe. Venusaur is a good check but it needs HP Fire / Knock Off to beat it reliably and still losses to fast Aegislash, plus it also gets worn down insanely easily.
- As far as having Mega Heracross, Mega Medicham (who already damn lost its "power", or should I say "hype" anyway), Mega Gardevoir, Mega Gallade, other Pokemons (NOT) losing their "usage" (but simply having one more Pokèmon to consider when building a team around them), I can (not really) see the concern about this (however; if a Mega or non Pokèmon is already in the need of specific support for handling some threats, wouldn't that still warrant an inferior usage compared to other Megas-Non who require LESS support? Like Metagross, Landorus-I, Charizard-Y, Keldeo, etc); so what if people MIGHT end up (POSSIBILITY) using Gardevoir/Gallade/Heracross less but ALSO end up using Mega Metagross, Mega Lopunny, Mega Altaria less (which people seem to be complaining about)? My major complain is that you people just keep banning things to "balance the equation" (which still remains unbalanced anyway).
The fact Aeigslash cripples things like Metagross, Lopunny, and Altaria is not reason to bring it back down, quite the opposite. You don't bring down one broken 'Mon to check more broken 'Mons, you ban the ones that are overpowered or overcentralizing. You'll never see something like Lugia come down to OU just so Landorus-I isn't broken, or anything ridiculous like that. Broken checking broken is a terrible philosophy and isn't at all a legit reason to bring any 'Mon down. You bring a 'Mon back down if it isn't going to be insanely overpowered or overcentralizing, and Aegislash is definitely not a 'Mon that should come back down.