Not to speak ill of the combat people remember from the old games, but I found combat in this game to be one of the weaker points, and to be rather boring kiting or circle strafing everything to death. Still, I think there ways to spice things up without changing the formula too much. For example:
-An enemy with a familiar mechanic where you have to stun them and actually physically remove and item from them.
-An enemy that has some sort of vital part that must be destroyed on all four sides to kill.
-An enemy with a weakspot on the back that you can only get to when they do a charging attack like the ogre.
-An enemy with a weakspot that'll shift onto random sides.
-An enemy that'll charge up a strong AoE that you'll have to run away from, but will leave it temporarily stunned.
-An enemy that'll occasionally charge up a strong attack that will backfire on itself if you interrupt it with an attack.
-Then there could be elemental based ones, like burning a mummy, or freeze and smashing a slime.
-If the devs want to be devious, make an enemy that leaves a damaging trail behind.
Of course a lot of these are some variation on having weakspots, something which in of itself might seem overdone, but I think it's a good mechanic that works better than the monotony of smacking something until it's dead. If we did, want to change things up a little, though, they could add blocking. After getting a feel for how an enemy attacks, you could click on your shield to block an attack, and stagger it to leave it vulnerable. Arrows could be deflected, and magically enhanced shields could reflect projectiles back at enemies.