I actually had a guild mate ask me last night what spec she should go when she gets her mage to 80 and wasn't sure which would be better for that gear level, so thanks for the heads up on that. It does make sense, though, since Arcane can use a very mana intensive rotation in heroics to squeeze out extra dps since fights are all very short.
yeh i forgot to mention that...(i was intending to)
i haven't had any problems spamming AB until MB procs and then rinse and repeat.
on boss fights i get away with blowing all CD's and trinkets from the start.(with mirror image) only once have i had to use a gem and a mana pot but that was in VH at last boss after the mana drain.