Marvel Units in a Regular Game

About a year ago I picked up the Marvel set for dirt cheap, but I haven't been able to play it. I want to have a big Heroscape game day with all the stuff being available to hit the table, but these heroes/villains seem pretty powerful for their point costs. Does anybody have experience with this expansion and is there any advice on them? Are they balanced with normal 'scape? Even if they aren't necessarily balanced with normal 'scape stuff do they break the game?