Who should be at the top of the healer stack?

Ghostcrawler reported in another thread:

Q u o t e:
We didn't want to nerf the amount Lifebloom heals, but we were concerned druids would jump to the top of the healer stack pretty quickly with the recent mana changes.

So this begs the question, who does Blizzard believe should be at the top of the healer stack?

Hopefully, the intention is that the best healer in your group (5, 10 or 25 man) would rise to the top of the stack regardless of which class they choose assuming gear parity. But I haven't read that this is the stated goal of Blizzard. It is certainly the case that Priests and Druids have many more methods of healing than either myself as a Shaman or a Paladin. Does someone want to go on record with what Blizzard's policy is to what is the heirarchy of healers?

thanks,
zib