This is part of the mentality that I want to address. Yes, WHM/SCH is a great complement to one another, but the AST is neither of these two classes and we need to stop treating it entirely as if it were WHM jr. or SCH jr.

The fact that the AST shields overwrite the SCH, should just mean that AST are careful about when they use Aspected Benefic or Aspected Helios, mainly avoid using it on the MT as the SCH will already be using Adlo on them. But if the AST sees Galvanize go down, he can use Aspected Helios to follow up, and the SCH doesn't have to bother with popping Succor. Instead they can continue dealing with other aspects of the fight.