I run this setup currently, and ever since they allowed Entangling Roots to work indoors! - I can do most any instance without going feral - only exception is bosses that spawn too many adds.

Also, I'm not in moonkin form most of the time, I run as balance caster to be able to heal instead (pesky aoe damage). Entangling Roots really makes it a viable team for instances, since you can lock down the melee guys easily, and nuke whatever else does damage. The stun component on Starfire is pure sex.

I eventually specced the main feral anyways, since some bosses do hit fairly hard, and keeping aggro one 1 toon is easier to heal - and bear make a wonderful sponge for taking heavy hits.

Lvl 62 now, been in Winterspring since lvl 58, grinding Timbermaw and Winterspring Sabers - yes, I'm THAT nuts. 58-62 is purely from killing teddies and giants. Did Scholomance @ lvl 60, was loads of fun - ended up soloing Gandling as bear, since I couldn't keep the others alive when they were ported constantly - too much micromanagement. Bear just swipes down the mobs, beats on Gandling, gets ported, heals up, rinse, repeat.