AST has the best MP sustain in the game by far if you fish for Ewers and Spears, so there is really no problem there. It's MP sustain is actually so good that it can solo heal AoE-heavy stuff like Delta 4.0 without running out of mana, even when the entire party is eating a ton of avoidable damage on top of it.

SCH, on the other hand... now that class needs to major fixing...