I love mantras aesthetically and keep trying to find uses for them, with limited success. Then, when I see a guardian using their staff 4, I get jealous and wish my mantras did that. Some pulsing effect while channeling them—pulsing once per sec for the 3-sec channel—whether it buffs allies or hinders foes.
Effects could include, off the top of my head:
Pain: Bleed and/or cripple nearby foes
Distraction: Confuse nearby foes
Recovery: AOE heal (incorporate Restorative Mantras)
Resolve: Random boons to nearby allies
Concentration: Fury to nearby allies
Kinda shooting high in terms of power, but the 3.25-sec channel is risky and has a high opportunity cost.