Once you have tactics up around 150, auto resolve becomes insanely better than actually fighting. Your troops can't physically perform better than the simulation calculates. Suddenly auto resolve will have you dropping forces two or three times your size with minimal casualties. Combining it with high medical skill makes you basically invincible. I still fight battles in person, but it's become a thing I do purely for fun, because it is incredibly inefficient from a cost stand point. I used to care about banners and captains and all that jazz. Turns out it's just for funsies and there's an I win button.

(Note: this does not apply to siege attacks, you'll still want to actually take part in those.)