I'm looking for a link to the priest calculator I've seen that lets you input your talents (and other armory info, i think), and it will calculates the 'healing per mana' and 'healing per second' of each rank of each of your spells...
I remember seeing it in a discussion of weather Heal Rank 4 was a good spell to use at level 70 (instead of Greater Heal, I think). I'm pretty sure it was somewhere here on allakhazam.