Frosticus

Black Scorpion can help you out there. Poison ray helps your summons beat down stuff even faster. Enervating field, maybe some -res proc(s) and poison ray will have your pets taking down bosses and EB's fast enough that you won't miss containment damage. ill/rad isn't really an aoe combination so I wouldn't worry about high damage fissure or fireball. Fissure isn't bad for the additional control though.

Ill/Cold is hands down my favorite pairing for controllers, probably in the whole game. However, it takes a long time to reach maturity and while pretty decent with basic enhancements it benefits tremendously from set bonuses. /dark is good pretty much from the get go and stays strong the whole way. /cold can't really protect itself if you join a bad pug and you pull a lot of aggro with your powers so prepare to faceplant. /dark imo doesn't have as high of a ceiling as /cold but can arguably help a mediocre team better if/when things go wrong.