The people most easily able to tear someone a new one (the zerkers) are effectively having the few restrictions on this power removed. I can see why you'd propose that, but I think the powers would need a major tone-down. I don't think being perma-lagged by zerkers is remotely balanced.

Also, I really don't like the idea of one faction of battle being able to cut people off from mana sources. That means magi are potentially going to be without magic, as if assassins with tiger claw and dagger specs with hurl weren't enough. Not only that, but now the priest classes aren't as much danger because you can (a) gang them as a zerker, or (b) cut them off from their mana.