KB+M WASD is actually superior to just Mouse move+aim. It allows you to aim and attack while moving in completley different directions without the character stopping, rather than Diablo 1-3’s dated system where they conflict. If you had 2 people of the same skill PVP one with each setup, the WASD + Mouse would win every single time (if Diablo 4 allows WASD movement and pure mouse aiming).
It’s pretty much the best of both worlds of mouse vs controller. You get controller’s ability to move while attacking but mouse’s extreme speed and accuracy. The only thing better would be to use controller’s joystick to move with greater accuracy than KB with left hand and use mouse in right hand.