Prot or Holy are actually the best grinding specs IMO. If you are Holy or Holy-Prot but wear Prot/Stam/PVP gear you can do more spell damage to the mobs whilst getting uninterruptable (by which I mean no pushback) heals (unless they kick your spell school). I am not sure what the exact hybrid spec is but you may want to experiment with a talent calc.

If you do not have a lot of stam/tank gear go prot as you can spec for extra survival that your gear doesnt give you. Also, bring more than 1 shield if you can, mine broke after several runs and I had to repair at LHC.