I honestly felt that Diurnal AST was in a pretty good place now. Messing with the cards only has me worried, not happy at all so far.
I REALLY hope it's just a simple matter of potency/duration increase, no complete overhaul ;-;

As for changes to shields, well, we all knew they'd be coming at some point since Noct AST was so inferior to SCH.
Not much to mess up there.