Thanks! Is there a level where Black Resonance is given as a support ability? Or do I basically have to have multiple black mages in my party to reap the benefits?

That's a little odd. So which goes? And is the other null? Thanks!

When changing difficulty in game, the menu just says "Enemies are stronger". I've noticed a big increase in attack + magic strength, as well as a substantial amount of health. The enemies seem to still Brave/Default the same amount, however. Beyond that, I'd like to know as well!