The talented 51pt spell is Arcane Barrage. You may be thinking of the Missile Barrage talent though, which (at 5/5) has a 20% proc to make your next Arcane Missiles cast a 2.5s channel. I might think that you could do a 'not trying to go OOM from Arcane Blast' spam key something like:

/castsequence [nochanneling: arcane missiles] Arcane Power, [nochanneling: arcane missiles] Arcane Barrage, [nochanneling: arcane missiles] Arcane Missiles

I think that's how you use the channeling macro modifier, though I may be wrong, and I think you can spam this key for good DPS without severe mana issues.

Personally I'm all about group synergy so I went with a Frost spec with Focus Magic: 11/0/50 One-spell debuff stacking with Winter's Chill plus Focus Magic and buffed up Water Ele. It's a strange spec, I admit, and the first one I've made without Ice Barrier. But I figure she'll never be out solo-ing and I find Ice Barrier hard to use in group when multi-boxing.