Hand of Purity the first, Divine Protection the second, Hand of Purity the third. If you get a fourth your DPS suck and need to wake up.a mini-cool down for one of Meg's breaths (unglyphed divine protection could cover the other).
5BG 3HP WoG IS, to all intentions, Lay on Hands. I've seen it crit for over 600k and, with cooldowns stacked up (wings, priest cheat death), heal non-crit for about 500k. Use it wisely.