Channeling Divine Plea. No tank I can think of wants to do that being mana starved on a long Boss fight where he needs mana. In between pulls use full as I did find it helpful after some fights vs having to drink. This spell benefits Holy and Rets more than Protection spec in a Jam where we would normally need it. It seems to tick two times per 3 sec for the spell as per combat log.
It had a somewhat cool animation when it starts to channel and sounds like your summoning the class mount. You get this at lvl 71 from trainer.