After spending a little bit of time (mostly solo) on the 4.0 PTR, I worry that multi-boomkins for BGs will be inferior to Shamans. The stealth advantage will still be there, but I worry that the setup just doesn't have any punch needed for large health pools.

I think it will be possible to set up some cool rotations that keep people at range, but more than 1-2 enemies coming at you will be hard to deal with. There's no amazing ranged attack damage like the shamans have, and there certainly isn't the turtling defensive capability that the shamans have.

I have not tested out everything in a MB configuration, obviously. But I will say that the shaman changes appear to give that team comp a significant upper hand.