Resto druids were the least competitive and least taken healer in 25 and 10M heroics in WOTLK (barring holy priest but they have 2 healing specs).
4x the number of paladins, 2x the number of disc, 1.5x the number of shaman were healing end game heroic content (last I reviewed the numbers) and resto druids look to be headed in the same direction for cata.
Consider adding a glyph to make mushrooms a viable mitigation CD, barkskin castable on tanks…something to make it viable to bring rdruid in a 10 or 25 M comp and help break up the meta a little…