I think it's probably less worth it when you are doing 3 targets or less than when you have 4+ but PoH is still a great spell for raid damage from what I've seen. I might not always value it over PoM (especially not once I get 2set) In many situations but certainly not a spell to stop using very often.
PoH is 2.5 second cast, hits 5 players maximum if in group and in range.
Penance+PW:Solace+Smite is ~2.5 seconds cast, smart heals, hits 5 players regardless of group. And heals for more.
In what situation are you casting PoH over Penance->PW:Solace->Smite?