But isnt that kind of irrelevant because we dont even know about fairy moves yet ? (Actually its been irrelevant since gen 3 since the physical/special split but w/e)
Also Azumarril is very bulky. I doubt a unstab neutral steel move will do much against 100/80/80 defenses and certainly wont OHKO.
EDIT:
It also gets Ice Punch to hit grass/poison types on the switch VERY hard.
I said that they wouldn't get OHKO'd, though its very possible to kill them in 3 hits even without STAB.
Doing a comparison between Garchomp and Azumarill with Garchomp attacking with one of the more common Steel attacks Iron Tail, it does 115-136 raw damage, No boosts, no EVs no IVs.
If you can get one fully set up it causes major damage.
A +6 Attack Garchomp can One Shot an Azumarill if it switches in and has no bonus, though that is an extreme.
With enough speed, anything can really out do an Azumarill making it as I said, a Punching bag to stall for the right set up or, a more positive way to put it since Punching bag may be the wrong term. Azumarill is a tank. It'll be slow moving, can take a hit, and can dish out some major hurt, but these things are what gives it a major weakness to the speedy hard hitting foes.
All we have to play with are what if scenarios. But even still I completely disagree with the turing the meta game on its ear type of responses because even with these changes, many of the Pokemon effected aren't that great and alone don't make enough impact.
Steel losing Ghost and Dark resistance is a bigger change than Fairy types alone IMO. Metagross, Bronzong, and Jiranchi magically gain 2 more weaknesses that they didn't previously have before.
Only really good thing about Fairy is that they kill Sableye and Spiritomb as neither no longer have no weaknesses. This also opens the door for more Ghost/Dark types to enter.
