I have been levelling a Priest recently and have moved on to the Cata Dungeons last night. I've never had much problem along the way healing dungeons. Priest Healing is a ton of fun compared to Paladin Heals. I am having a blast. Every other time I get a tank that tries to push me to the limit I know I can keep up and still pull decent DPS with Atonement.
However, I've been having a hard time with Rapture. I'm not sure I'm using it at the right time. I didn't really feel it was a problem during TBC and WTLK cause my Shields stayed up longer than the mobs for the most part.
RAPTURE "When your Power Word: Shield is completely absorbed or dispelled you are instantly energized with 7% of your total mana. This effect can only occur once every 12 sec."
So that is the tool tip. Now what I would like to know is, how should I go about it? Should I be throwing PW:S every 12 secs? or Can I throw up a few? And What exactly does absorbed refer to? Since they've lowered the duration of our PW:S from 30 secs to 15 secs its gotten even more confusing for me? I'm assuming it doesn't mean till the Shield wears off?
Keep rapture on cooldown, if you don't have a shield up and raputre is about to come off cooldown, get one up on someone who's going to take a hit which will proc it. Keeping the mana inc from rapture is a crucial part of disc dungeon healing in particular i found when i played mine.