PRIEST TEAM PLAY:
Lets say you had say 2 disc priest that were completely dedicated to whoever the main tank was. These priest would go int>haste>mastery. They would completely ignore spirit 100% if possible.
Then using just the normal heal spell not using greater heal they would use Strength of Soul in unison to very quickly reduce the weakened soul time on the main tank. 4 seconds a per heal cast. if they both went haste>mastery, how quickly could they reduce the weaken soul effect? Finally consider if these 2 disc priest took turns toggling who would use PWS. They would effectively have unlimited mana in a raid environment. I believe that mastery absorption would scale better than spirit in terms of mana battery, am I crazy? Is this too hard to do? Will I make gladiator as Fire mage one day? All of these questions to be answered at some point.