My old rule was 1 healer for every 5 DPS. In heroic ToS I liked having their cd's more than their output healing so I ran 4 + 1 healers. Our raid is only semi-retarded; that said, there is unnecessary spike damage which adds the +1 healer regardless. We run 3 in heroic for some of the bosses but then hit Avatar and its back to 4-5.
So now we move on to Mythic, and I got to sit some people perhaps. This is our healing composition: Monk, Monk, Pally, Priest, and Shaman that is our top healers we all have viable second and some third specs. We are bringing up another pally and a druid but their gear is well below the 930 mark and has no secondary spec.
Atm, I am considering: Monk, Monk, Pally, and Priest for 20 mythic.
Any thoughts?