What I have used for a long time:
/cast Arcane Power
/use 13
/use 14
/castsequence reset=10 Arcane Blast, Arcane Blast, Arcane Blast, Arcane Barrage
With 5 different classes, I have no intention of trying to micromanage using Arcane Missiles on procs, but that would be the most ideal DPS. When I manually run the mage in solo mode, I always use ABx3, AM, and cast ABarr before the last missile from AM launches which results in 4/5s of AM and ABarr all benefitting from the ABx3 stack buff (AM only consumes the buff when the last missile hits).
The arcane mage is definitely a huge mana hog, but then you should also talent your Evocation cooldown to just 2 minutes, which is mandatory for any raiding. For heroics, you're not going to run out of mana on any single fight, so you don't even need to think about mana efficiency. That same lack of efficiency translates into very high DPS, though. My guild refers to my mage as "the DPS queen". Only a DPS DK gives her a challenge right now, mostly on trash and not so much on boss fights (multiple targets vs. single target).