One thing I noticed tonight playing my Wizard against swarm is using reverse attacks and and aoes really helps. I'd generate a ton of mana. Then zap all his stuff then use a big spell on him. Anything you can do to get them to waste actions helps. Set him on fire so he has to dowse his burn instead of buffing. Play decoys so he goes to disenchant them. Teleport a lot so he has to move a lot. Unpredictability seems to be the key against the swarm. A tactic I wanna try is baiting them all into a corner zone, walling it off then teleporting.