PoH is one of the most 'spread-forgiving' aoe heals out there.
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.