Disc PvE is fine - gheal should be you go-to heal as disc, heal is too weak as you say, but gheal is cheap with IF so that's not a problem. I've been healing 5 mans since I was 329 ilvl as disc and managed, even with 2.5% rapture.
PvP disc is broken, but I don't think it's just disc - PvP healing in general is broken, damage output vs healing output is way too skewed towards burst dps classes. The fact that disc has almost no escapes vs most classes doesn't help either.