I've seen a lot groups going with two healers, Bu our team is only started 10mans last week, so we not that geared and so on, is it ok if we stick 3heals for starts, healing blobs is easier at immersius and on protectors one our healers goes oom because some mechanics to be learned for ppl and they wont take that much damage later in tier so 3healers for first few bosses what u think?
If the whole group was experienced and geared (for the content you're doing) then two healers would obviously be the superior tactic, with the extra DPS allowing faster kills and phases to make it possible.
That said, it's preferential for farm. If you was to progress a boss, take as many healers as you need, most people take 3. We took an absolutely outrageous amount of healers for a lot of the bosses in SoO during progress.
Once you're all in good gear, you can cut down to 2 healers if you really want.