I have a team of Druids to level 42 right now and am still learning them. I can't really answer your question but can share my experience so far.

I went with the Feral tree up until level 40. Mainly because I was 'soft and chewy' and figured I would have a better chance using bear/cat and a lot of melee.The double edged sword of the RAF thing kept my gear in a horrible state. Couldn't keep up with gear and having enough gold for training at the same time. So Feral helped a bit with that.

As soon as I hit 40 I re-rolled my talents to Balance so I could get my boomkin. Wow, what a huge difference! I feel like a Mage with plate armor. Most of the time I can one shot (actually 5 shot) with Starfire two levels above me. For elites follow up with moonfire/faerie fire combo on the group of them and go to bear form. I can see how leveling will be a lot quicker now. I think I will just keep them all boomkin until further down the road and go from there. Not sure where I"m heading yet.