AST question:

[Palibun]

Nocturnal is a waste of mp and in most cases is arguably worse. I see some asts use it for dealing with big pulls, but if you have a good tank that uses their cds well then it's pretty pointless; the barriers go down so fast since tanks take so much damage. They're mainly helpful for, say trials, where you have two healers.

You can try playing with them a little; i once had a tank that would not turn their stance on, so i kept using aspected helios's barriers with noct. sect and it made the dungeon way more manageable for me, but it did also gut my mp pretty badly.
And once you get Celestial Intersection... at that point it's 100% useless, the cd timer on it is short enough that it covers the barrier market perfectly.

Maybe for raids and trials you can find some use, but for the most part it's pretty useless.

[Risvertasashi]

They're mainly helpful for, say trials, where you have two healers.

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.

[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

[Risvertasashi]

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

I guess that's a case where it may be equivalent, but you can accomplish the same thing on a wider range of content via regens.