Are we sure it's only cast on non-mana users? I wish I had some sort of proof, but I seem to recall that I've gotten the buff several times over a course of many wipes.
If it can hit everyone though, that would seem to support the strategy of grouping up around, specifically behind the demon, in order to receive the benefit of Kalecgos' Revitalize ability, which is a frontal cone based spell:
Breath: Revitalize - Spells - World of Warcraft