It's currently OP in PvE, so how do we fix it in PvE without effecting PvP?
These are my suggestions:
1 - Rapture no longer benefits from short-term (trinkets, Mana Tide, etc) spirit bonuses
2 - DA nerfed by to be 20% absorption on all spells, but DA triggers from all spell hits, not just criticals
3 - Spirit Shell now has a 3 min CD but each time Penance is channeled entirely the CD is reduced by 3 seconds 90
4 - The Spirit Shell duration now lasts 30 seconds.
5 - Archangel now restores 5% mana
6 - Evangelism now includes Power Word: Solace
7 - Atonement now includes Power Word: Solace
8 - Prayer of Healing now has a 7% base mana cost (from 13500 mana to 21000)
1) Rapture benefiting from short term spirit buffs is pretty ridiculous. I've seen logs where Disc Priests are getting 120-150k mana returns from 1 Rapture inside a Mana Tide + Relic of Chi-Ji / Spirits of the Sun proc. Both Relic of Chi-Ji and Spirits of the Sun can proc together due to the way their ICDs and durations line up, this basically guarantees a Disc Priest can generate a Rapture proc of 50k~ every 105 seconds which makes the spell far too powerful.
2) DA at 50% is ridiculous, not just on PoH but all spells. DA at 20% but baseline makes mastery a stronger stat (which is hard to balance because absorption effects are just better than heals). DA at 20% makes all spells 20% "stronger" which is fine because most of Discipline Priest skills are based around being 5-10% weaker, and at the moment Disc is pretty weak at tank healing and in PvP, Disc is even worse off. Passive DA on all spells I think will give Disc Priests more power in PvE. I might be wrong here.
3) Without the 4 piece tier bonus this would make Spirit Shell's CD (with Penance used on CD every 10 seconds) around 126 seconds. With the 4 piece tier bonus this would make Spirit Shell's CD (with Penance used on CD every 6 seconds) around 90 seconds.
4) To offset this nerf (mostly to those not using 4 piece tier) Spirit Shell now lasts 30 seconds so that the entire effect is met.
5) Archangel returning 5% mana now gives Disc a more reliable "healing" throughput CD, especially with my proposed DA change.
6) Power Word: Solace needs to be buffed to be "as good" as Mindbender. Simple as. Mindbender is the best choice for Disc at the moment.
7) Quality of life.
8) 13500 mana for PoH is a joke. Especially with how good Rapture is now.