Healing in raids might work as druids, however I'd say only in 25 man effectively. 10 man is generally possible in encounters as say PDK, since they are fairly easy, but icc would sometimes be hard, as you cannot really use the full extent of your skills with two characters at once.
Why 25 man? As druids you are usually healling the raid by spreading hots. I'm fairly sure I could handle Rejuvenating the raid fairly well, since you basically have 0.5 secs to retarget/move your mouse to the next target. (0.5secs is plenty of time for me, if it's not for you I wouldn't recommend it ^^)

With Priests, raid healling should be doable aswell, but I think it would be harder since you cannot simply "cast around hots".