Plea is a great spell when on the move - I even use it in raids and it's much better in dungeons where you never have more than 4 atonements up when you cast Plea.
In a dungeon when you're done with one trash mob and moving to the next mob, Atone the DPS with Plea while running, and use PWS on the tank. Then when you get to the next mob, Penance > Smite (or Schism > Penance > Smite) to heal the entire party.
Healers think a lot about healing *during* encounters, but it's important in dungeons to also think about healing *between* encounters.