I think the issue with druids is our fast spammable heal (regrowth) takes up a lot of mana, and our low cost heal (nourish) is so slow and does so little healing that I at least felt adverse to using it.
How I heal in dungeons is save regrowth for a boss fight, if your tank has decent gear they won't need it. Cast rejuv at the beginning, and then start casting nourish right away, and if they need it go ahead and let the cast finish and if not interrupt it and start the cast again to save mana. Keep rejuv up but save swiftmend for those "ohshit" moments.
I agree that healing seems a little more work intensive on resto, I had a lot of problems transitioning from disc priest healing (bubble, /afk) to resto, and resto definitely has a lot harder of a time coping with undergeared tanks, bad pulls, and insufficient dps. It is doable with some careful mana management but you have to be prepared to deal with those bad groups that don't understand that druids don't get dealt the same deck of cards at this level as other healing classes.