Circle of Healing, rank 5 : 550 mana, I cast it for ~1000 healing, currently no CD, instant cast.
Prayer of Healing, rank 6 : 1005 mana, I cast it for ~2500 healing, currently no CD, 2.9 second cast.
With a one second GCD, we're looking at CoH being used three times, healing for 3000 hp, while PoH heals for 2500 hp.
Perhaps if Blizz gives CoH the nerf for a CD of 6 seconds (speculation about a possible one or two second reduction exists, but for the sake of argument, meh), they could also give PoH the same mechanic that CoH has, in that it smart heals the lowest 5 party or raid members? That way, we have a spell that compares to a shaman's CH, in PoH, but also have the "Oh crap" resource aspect of CoH? Looking at the numbers listed above, doing this would make PoH exceptionally mana efficient, so possibly increasing mana cost or reducing healing, but not by too much, for the restriction of movement should be looked at as a drawback.
Thoughts? Also, please don't just flame my healing numbers...