There are different ways to run your Gliscor's EVs. I like this one the most.
252 HP / 184 Def / 72 SpD
There are others. You could throw in more into the Special Defense or Speed department or even take some HP EVs and distribute them to your liking. It is really just supposed to give Gliscor reasonable defensive bulk and enough to take a few Special hits, not like you'd want to leave it on those anyway.
Also, try Substitute to really stall Pokemon out, probably over Roost as Poison Heal is already a damn fine way to recover.