I am lvl 44 now with my MMMMP Team and I skilled in the arcane tree till arcane concentration & improved AE (I am using AE 90% of the time). I am not sure what is finally the ultimate best way to spend my other points. But i decided for going deeper in fire, at least while leveling.

Blast wave is nice additional to my AE and my fire spells (fireball, fire blast, pyro as initial) are pretty strong against bosses. Maybe when the trashmobs are getting more life, dealing more dmg and so on, i might swap into a deeper arcane spec or test out frost.

But this situation still not happend right now. Things running very smooth (and simple).