All of these changes seem so unnecessary and are only being done because of how badly proposed 5.2 Disc nerfs have been (the main culprit being PoH will no longer automatically cast DA and Spirit Shell no longer working with mastery).
Recall that the main problems we are trying to fix for Disc in PvE are that they are overpowered and relying too much on Prayer of Healing spam, especially in 25s.
For the One-Millionth time, that because it's the only flipping tool we have to heal AoE damage other than pre-Spirit Shielding the raid. GC said they were against giving us a new AoE healing spell (and even agreed that we're lacking in that department!) but felt it would be too big of a change for Priests to get use to......Yet completely revamping our crits and how Divine Aegis works is A-okay.
We made some changes to Divine Aegis, but we're not happy with them. Because of the interaction with crit and mastery, we worry Disc will be too crit-dependent and won't be strong enough when they fail to crit.
They removed Auto-Divine Aegis from PoH and now are worried that we won't be able to AoE heal in these situations....Well at least they have that insight! So instead of giving us a new spell they're trying to once again baidaid fix the situation by changing how our crit heals fundamentally work from every other healer and applying a +heal boost component to our mastery....Why not instead:
-Revert the Divine Aegis buff (from 50% of the heal back to 30%).
-Keep the Auto-PoH Divine Aegis nerf
-Increasing Spirit Shell's cooldown to 2 min but it now once again works with mastery.
-Keep the PW:Shield can now crit buff (this is actually really nice).
-GIVE A NEW HEALING SPELL to Disc with a 6-10ish sec cooldown. A spell that compliments the absorb/healing nature of Disc, and something that we can weave in with our PoH.
With my proposed changes: Disc would value both mastery and crit, and they would have something else to do during heavy AoE damage other than POH spam and PW:Shield spam (shakes at the thought of WOLK Disc raiding).
That seems a hell of a lot easier than nerfing Auto-Divine Aegis, removing Spirit Shell's function with mastery, adding a +healing component to our mastery, and fundamentally changing how our healing crits work from every other healer in the game.