My main is a war in a kara/za raid guild. We've did Ahune about 20 times so far.
We have yet to succeed with a deep frost-spec'ed mage (guys with the 40 some points in frost). The dps loss from having talents (and usually gear) aimed at frost damage is just too hard to overcome. However with arcane/frost 40/0/21 build mages we've managed to pull it out, but it they aren't the easier fights.
Our ideal group so far seems to be pally healer, lock (for seeding), fire mage, tank (war or druid -- really focusing on the single elite), and one random dps or augmentation char (shammy, rogue, hunter, another mage, balance druid, fury or arms war, ret pally, whatever).
It's really a simple fight in many ways. Keep the elite clear of the little mobs, have healer and 2 dps concentrate on the little guys, tank and 1 dps burn down the elite, clean up the little guys, go pound on Ahune's shield thing, and repeat that till he's dead. Stay away from the ice spike things that come up from the floor. But key to all of that is effective dps -- regardless of if you're dps'ing the non-elite adds, the elite, or the shield, the dps has to count. Heavy frost mages just don't put out the dps for this fight long enough, because their dpm costs are too high.