Arcane all the way. Only downside to arcane is mana usage, but i believe they buffed it last patch, less mana used, and when missile barrage procs (which should be almost every rotation in this new patch) it costs zero mana. Very simple rotation, 4 AB, 1 AM. I have my main mage dual specced Frostfire/arcane, and arcane is more consistent dps, pretty high, often fighting with my lock for top spot, usually second place though. As frostfire, its even more dependant on RNG. I have a very high crit rating, somewhere near 45-5-% with the shaman buff, so some fights, i do 5k dps, others i barely do 2. It can be difficult to manage the hotstreak procs, especially in an otherwise busy/tough fight, but I manage, I made a button that stops whatever im casting and casts pyroblast, and that seems to work fine for me, I just spam my main DPS key, watch proculas party chat for the proc, and then spam the pyroblast key. My shaman isnt as geared though, but he's getting close dps wise to my lock and mage. Both Mages and Shaman have a lot of potential, and I feel that it's best if you leave your team as it is, diverse. Your mage wants all the spirit gear, and your shaman do not, so if you drop a mage for a shaman, you miss out on more gear.