I run 5 different classes so I found watching for missile barrage too much to micro manage so this last time around I didn't bother spec'ing into it at all. My cast sequence is 3 x Arcane Blast followed by Arcane Barrage. I include all possible buffs in my macro: Icy Veins, Arcane Power, Presence of Mind, Mirror Image, 2 trinkets. My mage often tops the damage meter, so even if catching Missile Barrage would up my dps, I'm not too worried. She performs well, efficiently, and takes no babysitting...she's a single target machine. I like low maintenance.