I went arcane spec and have a similar class setup to you. I am rotating between two DPS buttons at my own discretion. I have one which is nothing but arcane blast spam and one which sends out an arcane bolt (and moonfires, shocks, etc on the others). When I need to save mana I alternate between the buttons a lot to reset the debuff. When I just want all out DPS, I do a lot more arcane blasts. I don't know that this is the best possible setup for him in terms of raw DPS, but that extra instant cast arcane move really comes in handy when I need to quickly finish something off that's running away, or when I'm on the run, or what have you. I can use fire blasts with a third button as well. Also, your burst damage will be great if you pop your POM and AP. All that and more threat reduction on the arcane tree have me sold on this spec.