Almost all healers are having mana issues (or at least, MORE mana issues than they used to) thanks to the revamp of downranking.

Even as discipline, I have a feeling that you're still going to OOM. The standard practice for healers is to utilize /stopcasting macros for mana efficiency -- i.e. Queue up a big heal, and if the tank takes no damage, /stopcasting before the heal hits and requeue.

Pallies FoL spam still has the mana return on crit, Druids have always been designed for keeping HoTs up on a tank, but Shammy and Priest healers are ooming much more quickly since they can't just spam chain heal rank 4/greater heal rank 4 infinitely anymore.