Disc is the best healer ATM, and will probably continue to be in Lich King. Shamans might come close to being competition, but Druids and Paladins will be far behind.
I have to come to the conclusion that you're doing something wrong. While they might not last as long as they used to before patch, that has nothing to do with them being bad, it's because everyone's DPS has about doubled. Priests are faring quite well considering.