This is probably the easiest mirror to beat. Bring all four element atunment spells and fire storm. Nothing else. Cast fire storm on him and he will die shortly. He will cast all the elemental atunment spells and most likly die before he even gets around to attacking you.
While I really like the idea of fighting a mirror image, I really wish the developers did a better job writing the AI. I know it's hard, especially with so many skills, but they ended up just having the mirror cheat or do strange things. I'm a monk and my mirror used a bow and hammer on me. That doesn't even make sense.