My current group:
Prot - Pally, 2X Elem Shaman, Resto Shaman, and Boomkin.
I am only interested in PvE.

Well I am just disappointed the the DPS from the Boomkin and thinking of replacing her.
The first thing that comes to mind is to convert the Boomkin to a healer and convert the Resto Shaman to Elemental. But I have heard that Druids are bit more difficult to box as healers.

I am not opposed to going to an different class. I see Fursphere dropped his Boomkin for a destruction Warlock. I am wondering why Warlock, why not Mage ? I am wondering if Fursphere had a good reason to go Warlock or was it just an easy change because he had a lvl 80 Warlock setting on the shelf. I was thinking Mage because I have some level 60's Mages setting on a shelf.

I am not very familiar with either Mages or Warlocks or maybe I should consider some other class? I am doing research on this topic and if any body has has quick thoughts they don't mind sharing I would love to here it.