I would go Alchemy to 485, for the Volatile transmute.
That transmute, will make you gold and get your Alchemy to the 525 cap.

Beyond that, Engineering is probably best for PvP.
If you'll do heroics with the team, one toon should have Enchanting for disenchanting.
Mining is more health, but DPS is probably worth more.
Similar idea with Skinning, you get some Crit but Jewelcrafting for superior gems or Blacksmithing for more sockets is probably a bigger bang for the buck, if you don't want to do the Engineering.

Not sure that Alchemy is #2 for PvP play.
But you get the free Flask which is nice.
Or double duration on anything you can make yourself, which is a nice profession bonus.