For my Disc priet, I use a /click macro, set up to click a priority, healing the target of my tank:

1. Penance when not on CD
2. a sequence that starts with 12 seconds of blank space, and then a greater heal and prayer of healing.
3. Power word Shield on a 15 second macro cooldown.
4. prayer of mending when off cooldown.
5. renew every 15 seconds
6. a spam prayer of healing button for AOE healing intensive encounters. otherwise, I leave it blank