So I've finally ground out the rep for the Oracle Talisman of Ablution yesterday. I'm not exactly sure in what cases I'll use it. I'm thinking solo'ng, and 5mans, and some PvP would make sense. I don't want to run out of mana in any of those cases. And I'm likely to get the killing blows in many of those circumstances. I have no idea if I'll use it in 10 and 25-man PvE. Probably never in 25mans. Maybe in some 10man situations, but rarely.
Right now I've got it on as a single gear item in my outfitter bar, so I can flip it in conditionally before a fight. 5mans and soloing make tons of sense. PvP will be tougher because I'll either give up my Mirror or my get-out-of-jail trinket. In trying it out a tiny bit, I'm getting 530 to 545 mana back per kill. That's completely unbuffed and just in slightly different gear sets. It's supposedly 5%. And yes, it's each and every time without seemingly any cooldown. I'll grab my gorilla and do some AoE farming. Heck, maybe I'll dig out two Tier-5 pieces and get some infinite farming set going.