Why people says AST is bad?

[Krixus]

AST are bad because:
Cant heal as good as WHM/SCH
buffs too weak/situational/short
Have MP issues
AST/AST combo seems not viable because Card buffs don't stack
lack of emergency heal skills

In before everyone realizes when Alexander raid (hard mode) comes out

AST are good because:
Heal almost on par with WHM/SCH
Buffs that no other healer has access to, can push through dps checks holding a strong card + buff
No mp issues because can shorten lumin. (refresh), and use ewer on yourself if needed.
AST/AST combo is even viable, because while you cannot stack buffs, you can have both astro's use a buffed single target card on their strongest dps.
Has a 40 second emergency heal that has higher potency than lustrate when used on a target with low hp, then follow with an instant aspected benefic.