I'm torn. I question whether a 0/53/18(Deep Fire with Icy Veins) or a 14/57/0(Deep Fire with Spell Impact) will be the better build.
On the one hand, you have:
3% hit
Icy Veins
13% reduced mana cost
A snare on Blizzard
On the other you have:
4% more crit with Pyroblast(nice synergy with Hot Streak)
10% of all spells are free
6% greater damage on both Scorch and Fireball
Firestarter
Focus Magic
So I'm left wondering if 3% hit and Icy Veins truly will outweigh 4% pyro crit and 6% greater Scorch/Fireball damage. Or if perhaps it'll be a matter of scaling. Will the Elementalist build be the better choice early on with the Arcane/Fire build being better later?
I can't wait to see some numbers on this somewhere. I'll keep you all informed if I find any.