is AST a better substitute for WHM or SCH?

[Risvertasashi]

SCH is really powerful ATM so I would recommend AST + SCH.

That being said, if true unadulterated raw heals is required, AST + WHM is the way to go for Medica II + Aspected Helios stacking for raid damage.

I think maybe a lot of SCHs are used to maximizing DPS... but one that focuses on heals really can be very effective and is something to see. On the other hand, stacks and CD timers do limit them, but there's little that a succor beforehand and indomitability afterwards won't handle... and there's whispering dawn if even more raid healing is needed.