23 kills on my mage and no arcane loops :-|

Anyway, the way I do him is simply run in and nuke. When he starts mirror (DBM will tell you) - hit follow and run around the room like a headless chicken while instanthealing (I use PoM, renew and CoH). When mirror is done, resume DPS. At some point, after 1 or 2 mirrors (depending on your luck) he starts unleashed souls (creating all the immune mobs), I switch to concentration aura, blow my cooldowns and burst him.

At some point he'll either start mirror again, at which point you simply hit follow and run around until it's done while healing, or he'll cast wailing souls (frontal cone shadow damage).When he start's casting wailing souls (again, DBM will warn you), simply run behind and resume dps. He should be close to dead at this point, but even if he's not simply rinse and repeat above strategy.