I'm running Incanter's Ward and Frost Armor (like my normal raiding selection) because I don't have time to Evocate.
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I don't WANT to play any other specs.
All my damage is in ABarr, and as I'm full Mastery it takes an age to cast as my small amount of Haste is scaled down a lot. Any time wasted stopcasting is just asking to fail the wave, so that's not an option. The only "quick" spells I have are my instants Fire Blast and Arcane Barrage and they do very little on the move.
Except Frost Bomb. See above for info about ABarr.
I'm having trouble with just one thrower. Again, requiring constant movement from a turret spec is bad design.