you can make the mobs crouch spam when you land crits, bunny hop, combat role, juke left and right, sliding mechanics. a combination of them to totally do you over.
you could also give them a walking speed and running speed which they change between making them more unpredictable.
that took me 2mins to think of. if i was a paid developer, i could think of more things.
instead, they increase health bars. top devs!