this is what i have my priest specced as...although i haven't changed him out since i started boxing, but he has a shitload of +healing and a 15k mana pool
with mostly epics and a few blues. i only have two macros set up for him...

1.) /target (insert main's name here)
/cast Flash Heal

2.) /cast [target=focustargettarget, help, nodead, combat] [target=focustarget, help, nodead] [target=target, help, nodead] [target=player] Flash Heal

The first one is a backup when he targets something else for some reason and the tank needs a heal...
The second one will:
1. The target of whatever your focus is targeting when you are in combat. So in combat if your main is tanking a mob this will heal the target of the mob, either your tank or whoever it is beating on. Out of combat this is ignored.
2. The target of your focus. Whoever your main has targeted will be healed.
3. Heals your current target.
4. Heals yourself.


Unbreakable Will 5/5
Silent Resolve 4/5
Imp Fort 2/2
Inner Focus 1/1
Meditation 3/3
Mental Agi 5/5
Mental Strength 5/5
Diving Spirit 1/1
Imp Spirit 2/2

Imp Renew 3/3
Holy Spec 5/5
Divine Fury 5/5
Holy Nova 1/1
Inspiration 3/3
Imp Healing 3/3
Spirit of Red 1/1
Spiritual Guidance 4/5
Spiritual Healing 5/5
Holy concentration 3/3