I did this on my 5 pally team pretty easily once i figured out what the heck was going on, used my half dmg bubble on the first big elite add that spawns so i dont get owned by the aura dmg then just run around in circles using seal of wisdom and spamming consecrate and divine storm and follow

its pretty easy, just let the npcs knock down ahune till his "core" comes out then finish off whatever adds with your aoe while you run to the core and dps it down fast, usually takes 2 rounds of phase one to do it