Regarding AST

[Braven]

Ast rn is not in a great spot. It does 700 less dps than Sch or Whm and its utility barely makes up that 700....

Looking at DPS without considering HPS (Healing per second) is worthless. AST does less damage because they heal more than the other healer.

AST has the strongest global cooldown heals (higher potency and instant casts) than the other two healing job. The best of the best will take advantage of that and have the AST handle more than 50% of the healing workload.

[KDSilver]

AST has the strongest global cooldown heals (higher potency and instant casts) than the other two healing job

WHM still has Cure III, and Medica II is still more powerful than Diurnal Aspected Helios.

Ast don't "heal more". He "has to spent his time healing through his GCD" instead. He lacks of oGCD healing.
So his dps will always be worst because any gcd spent on healing won't be on dps (of course).