I just looked up the quest info that starts the Doomguard chanin at http://www.wowhead.com/npc=14463#comments

This quest is being removed in 4.0.1 with spell "Summon Doomguard" learned at level 58. The Ritual of Doomguard is no more.
Looks like it's trainable with the latest update.

Oh and btw, thanks blast3r for the thread... just another thing I've missed with tunnel vision while leveling up!