Aside from being instantly destroyed by fear bombs of any sort, multiple frost mages pull off ridiculous shatter comboes and keep a massive amount of people almost permanently frozen (3x water elementals, 3 frost novas, 3 frostbite procs, and cold snap to top it all off) and multiple fire mages have very high impact procs as well as a possible pom+pyro if you dump 40 into arcane, although they are far too squishy to be anything other than a gimmick bunch that have a large (but counterable) multiple PoM Pyro every 3 minutes.

Frost is the way to go, imo. All the freezing effects give you time to work out all the nitty gritty stuff like your toons facing the wrong way or getting pwnd by melee. I personally use all blinks at the same time but I have to hope that my attacker doesn't stun me with one facing a different direction from the other 2! Plus icy veins gets rid of the annoying hunter pet pushback BS.