The class-specific Monk achievement Meditation says that I need to "Use Mantra skills to grant a beneficial effect to an ally 200 times."

I use mantras constantly and renew them as soon as they wear off, but I never get any progress towards this achievement. I've tried every mantra I have. I don't know what I am doing wrong. Do followers and other following NPCs not count as allies? Are my Mantra skills granting no beneficial effect to my allies? Is there a specific mantra(s) that I need to be using to get progress on this one? Is this multiplayer-only?