I can get to phase 3 of the fight after that his attacks are so frequent that I don't get a chance to cast and eventually I make a mistake. I'll try this rotation - Bliz3 Thun3 Fire3 Fire1 F1 F1 F1 F1 F1 B3 and repeat. Usually I don't get to cast so I don't get any damage done. Often I have to interrupt my cast so I don't get to do damage.