In case you didn't know, Blizzard admitted that Arcane is a bit weak DPS-wise at the moment. And indeed, when I changed to fire, my DPS went up by at least 50%. For those (if any) that are still Arcane specced, I encourage you to at least try out one of the other specs in PvE. Frost is supposed to be OK too, and they said they would boost Arcane damage in a future patch.
Ordo Malificum