The skills not stacking won't force Nocturnal. Nocturnal fails because shields aren't necessary in 90% of encounters, especially with allies who avoid avoidable damage.
If you don't need shields, then having them is worthless. So the sect that boasts higher healing numbers wins.
Nocturnal can't be forced unless shields are forced, and forced shields are eventually circumvented with tank cooldowns and gear progression.
AST just needs a singular healing kit, with some regens and some shields, and no bogus 'dichotomy' shoehorned in.
The same with WHM, and SCH, and the next healer.