Keep in mind that Aspect Benefic is 2/3rds the cost of Adloquium. It would be an incredibly powerful spell if it inherited the boost of the shield's potency on crit for a fraction of the MP cost. Noct stance is there to fill the role of preventative healing. It's a big thing in raid scenarios where there's a mechanic that needs a large amount of mitigation to survive its impact. Think t13's Gigaflare. Dirunal Sect isn't going to do much when the boss is one shoting the group. So you need nocturnal stance to soften the blows of the raid killing ability (Or maybe for mechanics like T10 prey).
Pretty much, Noct for raid (If WHM/AST); Dirunal for everything else I guess.