regirock: saying specially defensive regirock is nonexistant is hyperbole; it is used almost as much as 252 atk regirock and players like me still use it pretty often. the two (252 atk vs 252 special defense) sets are indeed pretty similar, but i dont think we should remove useful information for no particular benefit. it's still plenty good for helping regi tank special attacks from the likes of gardevoir, rotom-frost, and such. sunny day support set isn't that good though; that should go under 252 special defense ac. i would also put curse as a slash in regirock. such a damn useful attack on regirock in numerous situations i've been in. twave i agree with going in oo.
carracosta: liechi is still good despite hail, although it really hampers its effectiveness. still deserves a set, but the last set in this hail meta. non hail meta def deserves #1
emboar: mixed is /ok/. sub + 3 attacks is pretty cool; deserves 2nd slot imo.
gardevoir: agree with zeb
gorebyss: agree with zeb & dingo
haunter: agree with zeb
kangaskhan: agree with zeb. fake out is still really good on kanga (it has saved my ass so many times), but i wouldn't mind moving it down a slot or two. it shouldn't be slashed though. no reason to make it slashed b/c there isn't much that great to use with kanga.
sawsbuck: agree with zeb