Improvement to Time Dilation and Celestial Opposition in NOCTURNAL only, is the sole buff I'd give AST.

WHM should get a trait amended to Cleric Stance to finally give them some base accuracy to stack with, while having to gear towards the main healer slot (this allows for more piety melds over accuracy.) Why should WHM get this buff and not AST? None of a WHM's tool kit can 100% not miss. They also originated the skill, so something extra should be expected for them.

In general, the healers are balanced, as healers. As DPS, I feel AST is weaker during AOE, but on Single target, they hit fine. They could give Nocturnal Celestial Opposition something for this, but its certainly not killing off AST worth, since a Balance/Arrow/Spire/Ewer on a AOE DPS is their own AOE contribution.