Pretty much everyone who has posted on AST has entirely missed what those core issues are.
Diurnal is intended to make AST more like WHM by copying Regen + Medica II but it falls flat because AST lacks all the other tools that makes WHM as powerful as it is.
Nocturnal is intended to make AST more like SCH by copying Adloqium + Succor but falls flat due to lacking all the tools SCH has to capitalize on those Shields.
It is, in my opinion absurdly simple to correct. Roll Diurnal into Nocturnal.
Make it so Regen ticks come with an equal sized shield application for its duration. They still wouldn't stack with Galvanize. Turn Neutral Sect into a cooldown that converts the total potency of the Shield+Regen on aspected spells into single bomb heals.
Beefing up potency is just a bandaid on the gaping wound caused by the Sects.