I did some testing with a practice dummy, and tried
Code:
/castsequence Arcane blast, arcane blast, arcane blast, arcane missiles, arcane barrage
as well as that same basic rotation manually. The DPS numbers weren't different by much. I mostly use the sequence on trash just cause its easier. On boss fights, I do a manual rotation and as long as i remember to throw in arcane missiles, I dont go OOM too fast, and with the changes to mana regen, my in combat and out of combat mana regen is identical.

I don't bother waiting for the arcane missile haste proc, I just cast away. Usually 1 or 2 and often all 3 have the proc, but what I do, is if at least one did the full proc, I just interrupt the others and go back to arcane blast. It doesn't do as much dps as the blasts anyway, so if it doesn't go off in 2 seconds, I just move on. Also, I found that throwing arcane barrage helped a lot, as that does quite a lot of damage for an instant cast. I also throw in PoM Pyros whenever its up, and I use Mirror image often too. It's amazing the difference a little gear makes though. I have 3 mages with identical talents and macros, with the exact same spell rotations, and the one that got into more raids and has a few epics consistantly does 200-400 DPS more than the other 2. I think arcane scales very well with gear.

Once I get enough gold to buy cold weather flying (yeah, I don't have it yet, luckily my guild has a lock...) I will save for dual spec, and try a frostfire bolt build. Or, I could try 3 experimental builds, and test it on a dummy, and respec the other 2 to whoever does the most dps