Boomkin lacks heals in their DPS form.
And lose a lot of defense out of Boomkin.
But if your focus is larger battlegrounds and PvE, they'll rock.

I'd actually look at Feral Druids.
In 4.1, the Feral Roar (83 spell) will break roots AoE for 8 seconds (Dash will too).
And you can round-robin that for 32 seconds of immunity every 2 or 3 minutes.
Berserk doesn't deal with fear anymore, which sucks... but only shammies are really better than anything else for fears.
Ferals have more DPS, than anything I've ever boxed; they're sick in a good way.

If you were doing Priests...
I'd probably go dual spec on each.
Shadow and either Disc/Holy or Holy/Disc.
Then you can retain mobility, and mix and match how much healing to dps you want.
Probably 3 DPS:1Heals, most of the time.
But you could run 4x Heals now and then, too.