As someone who has been bashing his head against A4S for a few weeks now and pretty much feels like quitting until 3.1:

The difficulty jump between A2S and A3S is completely ridiculous. There needed to be at least two more bosses of gradually increasing difficulty in between them. Recycle models and mechanics if you have to, but the 4 boss structure should have died with Coil. Also, extreme primals should probably be a bit stronger now that we have Alexander Normal modes - the game is starving for medium-difficulty content. Alex normal is way too easy, primals are irrelevant because of tomestones.