It really depends on your raid, your tank composition, and your hybrid healing CDs. You're going to have to do a lot of finding out for yourself, and taking what other people suggest with a grain of salt. Nothing is clear cut, just because some people can 2 heal it doesn't mean you should.
For example, we spent a lot of wipes 2 healing Garrosh since so many people recommended it, but when we switched to 3 healers, we made so much more progress and killed it in few more attempts. We also have zero hybrid healing CDs most of the time.
As for heroics, we've 3 healed Immerseus and Protectors so far. Plan to 2 heal Nourshen and Sha of Pride, and probably 3 heal Galakras.