Again, I stress that pre pulse aoe, using a PoM (and sanctuary, if all are stacked) gives you passive healing while you stabilize the raid with PoH and CoH. Double points if people also click your lightwell in those phases.
Outside of pulse AoE, PoM is and has always been a crapshoot. You may cast it on a tank, it shoot to a rogue who needed healing at the time, but then rng dictates that he doesn't take any more damage before your next PoM cd is up. That's why I suggest casting it on CD on tanks on non ape phases and why I use it pre PULSE aoe, because that is sometimes the only way you will see every charge used up and used efficiently while you blast the raid with your big heals