Well, I think they could make a start by removing the lower potency compared to WHM / SCH. Even if the potencies match, ASTs don't have the rest of a WHM/SCH kit that makes them what they are, so it's not like they'd be outclassed (especially given AST's lack of healing related cooldowns). Without the ability to freely switch between sects they may have shot themselves in the foot with ever making AST a desirable serious end-game healer. Instead of being the inferior middle-man of both existing jobs they should've given them a unique healing mechanic. The cards are great and refreshing, especially considering how streamlined they've tried to make other jobs (mch isn't that dissimilar to bard, every tank now has an enmity combo and a branching-finisher 2nd combo etc), but we don't have dedicated support roles in this game, it is a healer. It *can* heal all the current content, but not without considerably more stress than the others. Stress the entire party will feel.

Considering they're half-Time Mage anyway (Gravity, various timer-tinkering skills) I don't know why they didn't run with that theme in the healing department too. Maybe make them a primarily HoT class, with skills that can consume the remaining ticks for a quicker burst heal, extend them much as they can with Time Dilation / CO etc. A couple more intersting CDs like Synastry...