I usually do arenas with my mistweaver monk friend, would that impact the choice at all? Also I'm heroically raiding as MS survival atm so would have to relearn MM, would that be worth the time investment? I do tire of becoming dead whenever a half decent team pops up
Agility, Agi/Crit and Agi/PvP Power should be your gemming choices. Some don't bother with Agi/PvP Power gems and opt for just Delicates there. Gear choices are fairly straightforward, if you can get Cruelty, get it.