The design philosophy behind Priest Healing in SoD has been very underwhelming, and the most recent changes to the new Healing Priest tier set bonuses suggest that gameplay can get even worse if concerns are not promptly raised.
In Phase 3, the rotation was CoH and PoM on CD with FH as filler, while strategically building Serendipity stacks in anticipation of heavy Tank damage (GH) or raid damage (PoH). This is where I started advocating for the removal of the party restriction for PoH to enhance gameplay in the new 20-man raid environment. Serendipity and any party PoH were introduced in WotLK together and were always meant to be together. If the reasoning behind not allowing this has been that CoH + PoM is too strong, then simply tune the numbers and please allow fun to be had.
In Phases 4 to 7, when not running the arguably boring PW:S spam spec, the rotation was the same as in Phase 3 except FH was replaced with BH, an unimaginative Rune that removed part of the strategical building of Serendipity stacks. I kept advocating for any party PoH throughout these phases to provide a viable alternative to PW:S spam. Instead, PW:S was gutted in Phase 7 with little warning and every Priest was pigeonholed into the same spec that had barely changed in 4 phases.
In Phase 8, we will either play PW:S spam again due to the new tier set bonus (which the devs previously said they did not want) or the rotation will be the same as before, except that now the 2-piece set bonus of the new tier effectively replaces Serendipity. This removes any strategy behind the building of stacks and renders the Rune virtually useless while avoiding the elephant in the room (i.e., party-only PoH).
It feels to me like none of the Priest Healing set bonuses have changed the gameplay since the beginning of SoD, unlike Shadow Priest AQ tier set bonuses for example. They have only changed the numbers in various ways and have instead taken away from the gameplay over time. Priest is the class with the most baseline healing abilities in the game, yet abilities like Renew, GH, and PoH are barely ever pressed in raids. This new 2-piece set bonus only works with Surge of Light, taking away the option of running Power Word: Barrier. Another good example is the new set bonus that enhances Spirit of the Redeemer, again taking away the option of running Pain Suppression.
Priest is the only class in the game with 2 healing talent trees. As such, Priest Healing should warrant significantly more design love and consideration (and more Runes) than any single spec of any class in the game, which I don’t believe it historically has. At the very least, there should be multiple distinct and viable healing playstyles, namely Holy BH and Discipline Soul Warding with potentially a way(s) to make Penance sometimes viable in raids (any party PoH would remedy CoH being so indispensable).
It’s not too late to make Priest Healing fun in an iteration of the game meant for trying crazy & exciting stuff. Yes, I am looking at you, Priest ZG class trinket which has unfortunately been forgotten.