I would just play as the healer, target the mob to be DPS'd, and heal with Healbot, or a separate spell bar with just healing spells. DPS as normal, and click heal Or set your focus on the healer to the tank, or whoever else you are assigned to heal, and use macros for that.

I find healbot invaluable. I use it when I need a quick heal on someone other than the mob's target, so I just mouse over to my priest and click the appropriate health bar. I've never played a resto druid, but I think it's all about keeping the HoTs up, so that should be pretty easy to macro in /castsequence [target=focus] lifebloom,lifebloom,lifebloom,rejuvenation etc. Something to that effect.

When I was running a priest and 4 mages around, I did all the dps via keybinds and had no priest spells in bar1 for bosses, and bar2 had SW:P and Smite, etc to help finish off trash. Now I run with a paladin main, and only heal with my priest, zero dps (well holy nova does some lol) and I do it all with one huge /castsequence macro, tied to all of my DPS buttons (same macro on 7 buttons, keeps the same part of the sequence) so I can manually do my mages DPS rotation, but keep the heal sequence rolling. I have a lot of blank commas in my macro, so if I need a lot of healing, I press the button faster, if I dont need much, pressing once every GCD suffices. I also manually add a heal or two when necessary, and for AOE heals, but for the most part, the macro does the job perfectly. I use /cast [target=focustargettarget] so it always heals whoever the mob is attacking, which has saved my behind on more than one occasion. And my manual buttons, are small heal on aggro leader, big heal on aggro leader, small heal on focus, big heal on focus.