Ultimately the reason Disc Priest is C-Tier is their immense struggles at keeping groups topped up and having enough throughput healing on a per-pack basis. While tanks are getting stronger as a whole this season, they do still require throughput healing to keep them propped up. This means that Disc has to throw more
Темное восстановлениеs into their target to keep them alive.
Additionally, Disc does not have great upper bounds for potential damage output as a lot of their damage is passive. While this is great for raid as it generally translates to a lot of free DPS, for M+ maximizing the time you can spend DPSing from the healer position is an integral part of the game. That coupled with their lackluster HPS throughput are the reasons they are C-Tier.