AST's weakness in end game

[technole]

You're also forgetting that, AST MP costs are lower for spells of the same potency as WHM. That means you spend less MP during a boss fight as a AST than a WHM, meaning their MP management is very much on-par with each other

Not to mention AST should be taking advantage of their toolkit to dramatically cut MP costs of skills during key moments of a raid. Lightspeed and Synastry help tremendously.