You think that's OP, one Pokemon can poison even Steel and Poison types (Toxic everything!), another shuts down priority moves!
Gen7 seems to be all about giving a big fat middle finger to the current metagame.
It all depends.
For this mon, its ability sounds OP but if its base HP stat is Shuckle tier, then it's not gonna do much.
For Corrosion (the ability to poison anything) it only really is good on a staller mon, so if the mon who has Corrosion is an attacker, it's a pretty meh ability.
As for shutting down priority moves (who has that?) if the mon is slow or generally is in an archetype that doesn't care about priority (i.e. not a sweeper) then it's not that good of an ability for that mon.
