There is a new Glyph for holy priests, which came with the 3.1 patch. Its changing the cooldown of the guardian spirit to 1 minute, if the spirit doesn't have to give his life to his protected target:

Glyph of Guardian Spirit

Use: If your Guardian Spirit lasts its entire duration without being triggered, the cooldown is reset to 1 min.

With this glyph you can keep your guardian spirit up alot which will boost the healing output on the target alot since it's 40% more healing in the time the guardian is active.