Zul'Drak Ritualist worth including as a singleton in your deck? Only played in 0.4% of decks according to HSreplay but is surely the best (and only for a lot of classes) tech against ress priest, the most 'hated' deck right now? Isn't too bad a turn 4 play anyway and normally survives with 4/5 health. Can be problematic against quest hunter (very rarely play these) and zoo lock, but if you can wait until you can deal with the summons to play it then its a solid taunt.
I've seen it in a Disguised Toast video (man that guy is annoying) in a build specifically designed to beat res priests. He lost the match.
It's an *ok* tech against one deck that is moderately popular. I'd probably skip it, though. It's just too niche, with too much of a chance to bite you. I'd rank it alongside Unseen Saboteur. It's an interesting tech, but just not good enough to occupy a slot in a deck.
I discovered it against a big priest from Tortollan Defender and thought I should add it to my singleton Shaman deck. I won that match easily, especially thanks to both devolve and hex as well. I haven't tried it yet though but I might replace tortollan defender with it but the meta is too aggressive right now for it, I think. Res Priest is like 1 out of 10 opponent in wild right now, it's overwhelmingly Mech Paladin and Aggro Mage and you're not helping yourself by giving those guys more minions.