I'd like to see lightspeed changed to make all spells instant-cast for the duration, and have the cross-class changed from thaumaturge to arcanist, so AST can cross-class virus and eye for an eye. Being the only caster without those two feels gimp.

Spread should work out of combat
Shuffle should give one of the other 5 cards
You should be able to change stance in combat
Nocturnal Sect potency buff should apply to all spells, not just heals.
Draw Card cooldown should be reduced to 15s
Aspected Helios and benefic regens need to stack when cast by other AST, similar to how regen from two white mages can stack.
Benefic2 proc should include a mana cost reduction, either 50%, or 100%. As it is now, the procs are mostly ignored, or saved for predictable burst healing to squeeze more potency out of Essential Dignity.

Even with those, I still feel AST would be inferior to scholar in almost every way, but at least they'd be comparable.

The primary thing that AST are missing, are cooldowns to deal with spike damage.
Virus and Eye would help, but aren't really enough.
WHM gets: divine seal, presence of mind, virus, eye for an eye, benediction, tetragrammaton
SCH gets: lustrate, sacred soil, indomitability, virus, eye for an eye, fey illumination, fey covenant
AST gets: lightspeed (questionable), essential dignity, disable (questionable), bole, arrow.

In fact, the only one that AST can actually rely on, is Essential Dignity. Which, is a fantastic skill, except for its 40s cooldown. Used on a Walking Dead DRK, or Holmganged Warrior at 1hp, it seems to be a 1000 potency heal, which is fantastic. Outside of that, however, is nothing. I don't count collective unconscious, as it's not practical to use 99% of the time. (or maybe I just don't know how to use it).