AST question:

[Averax]

Even in this circumstance, regens are still generally better. You'd only want to use Noct if there are attacks you absolutely cannot survive without a shield, and it happens so often that Neutral Sect can't cover it. Otherwise, you're tanking your own MP efficiency to no particular benefit and putting extra load on your cohealer.

In low level content, specifically, Nocturnal Helios paired with Celestial Opposition can provide enough shielding so that your other healer doesn't have to really do anything other than dps for the next 30 seconds