The problem of PoH is not range, its the party bound thing. Plenty of ppl will be in range, but will they be in the same party?
That being said, I agree disc is decent for night phase - the constant dmg ensures enough aegis soaking. I dont have hc experience for that, so my opinion might not be for the "elite". I got about the same hps as disc/holy on the fight, reckon easier as disc, because I dont play holy on a regular basis and I dont get "in the zone" fast enough for an one shot boss. What makes the difference is GS - which helps all the healers, and you can use 2 for 2 breaths. Divine hymn also gives a 10% boost, since the dragon is likely to get ticks especially at the start, when hes at low hp.
Pixl Returned! Holy Priest