Well, at the levels we're talking, a shot for 150 damage will do it. 300 will kill most anything in the challenge. So once you get beyond that, it's really just bragging rights.

I mean, a solid offense is needed, but if you can outlast a caster's entire repetoire in arena, you've pretty much got yourself a win. There's not so much on the "run away, try again tomorrow" tactic.

For a Psion burning through power points with a schism up? You're lookin at 5 rounds. For a mage? about 5-6 effective rounds.