At the end of the day, AST should not be treated as a must pick for end game content. Of course it'll be difficult to get there, but everyone should be able to pick a job that brings it's own unique benefits to the party and not be in a position where a certain job is actually greatly eclipsed by another; therefore rarely even being picked or ignored. Currently AST is one of those job which is mostly an insta-pick so it definitely needs a few tweaks to bring it on more equal playing field with the other healers.