When healing gets nuts (meaning party damage - tanks taking lots of spike / peak dmg is trivial if your hps throughput is respectable) you end up throwing heals / shields frantically trying to keep people / hope alive. In this scenario maintaining any of the disc buffs that make the spec remotely desirable is going to be next to impossible.
My suggestion :
Allow Penance to ad a stack of Evangelism (per tick or per cast depending on how Archangel ends up) whether cast as a heal or a damage spell.
This allows healers to focus on healing during intense healing phases while being able to refresh their disc buffs. Aside from the atonement range and dilution of atonement heals by pets, I think this would solve alot of the issues players are having with Disc.
The cooldown of Penance ensures that it cant be over used and still needs to be weaved intelligently even when thrown as a heal. Being able to get mana return from a healing ability instead of being locked in to damaging a target in order to pop Archangel will help immensely in intense healing situations.
Interested to hear what Priests think about the suggestion, esp. those trying Disc on Beta.