Right now, healing as a holy priest feel a little bit unsatisfying for me, so i tried to find some ideas that would make it a bit more enjoyable (in my eyes) and competitive. Contrary to what happens with the disc spec we already have the potential of a satisfying gameplay with the serenity mechanic, but this gameplay is left aside because it is hard to play and not enough rewarding, while the sanctuary gameplay is easier, a little bit more powerful and better assisted by set bonuses and trinkets.
First i would fuse the two healing chakras (serenity and sanctuary) into one. We would then have a healing chakra and a dd one. While in healing chakra, each single target heal would refresh renew on the target (like serenity chakra) and each healing spell would reduce the cooldown of CoH (like sanctuary chakra, but CoH would then be nerfed to compensate for the healing increase of the serenity mechanic). We would get rid of HW: sanctuary but keep HW: serenity.
Serendipity should once again increase the healing of PoH and heal in order to feel more rewarding and to give us some more capability to heal single targets (tank healing or whatever). Also it could help making us on par with the heals of the disco spec that have the grace passive.
Escalade could have a chance to refresh renew on the player it heals while in healing chakra. That chance would be a little lower than the chance to have a SoL proc from divine star or halo to keep things fair (it used to do that in MoP, but a 100 percent chance is too strong and would make that the go to talent). Maybe it doesn't need to have a lower chance, because the SoL procs also gives serendipity when used so they have some kind of bonus in themselves.
PoM could have a chance equal to our multistrike to not trigger its cooldown (making multistrike something a little bit more interesting than just a flat increase in numbers) and maybe to also refresh renew when its healing is triggered (making it a spell worthwhile to be casted)
Divine hymn could be replaced by lightwell as a healing cooldown.
Lightwell : 3mn cd, 8 sec duration. healing done by the priest on the lightwell are distributed evenly on allies within 40 meters of the lightwell. Healing are increased by X percent. (basicly it would be a healing version of prismatic crystal, with range and duration comparable to the others healing cooldowns)
Also, i think that Guardian spirit should work on every spell that would kill a player but that a paladin can BoP in order to avoid that (molten torrent of flamebender for instance). It would gives us some real utility that a disco can't provide. And you can also lower its cooldown to 2 or 1 minute(s) (it could then apply a debuff to the target in the same way BoP do to avoid abuse).
Finally, the clarity talent could use some buff, especially its range could be increased to 30 meters instead of 10 currently, because right now the spell doesn't even really do more heal than PoH. The two things interesting about that spell is the non group restriction, and its interaction with serenity, but it's hardly usable in the current raiding environment. By increasing the range and doing the other changes i propose, you would then have a choice between a talent that give a group heal not restricted by groups and with the ability to refresh renew on the primary target or a talent that would give more PoM that also have a chance to refresh renew.
Any thought or proposition?