IMHO, friars are a hybrid class that should stay that way. There fore I think the best template for a friar should be (at level 50) 25 in rejuv and 44ish in enhance with a 34 or 39 in staff and the rest in pary. Can solo yellows and an occasional oj, heal as secondary healer very well, primary heal if you have to in a pinch, and have the buffs to make yourself and your whole group better. this is the best friar spec for groupability and flexibility for a friar i think. Keep your gear yellow and oj and maximise your bonuses etc to keep you as close to caps as possible.
I'm only a 42 now, but have had no trouble tanking, primary healing, assisting in both, in both PVP and PVE. I have good groupability in both areas as well. Kind of the definition of hybrid class right?