As of now the worst part of using a mouse and keyboard is not having a neutral stance, there is no deadzone.

A simple solution would be to have an inner and outer circle you can move your mouse around in, simply when you have the cursor inside the circle, you are in a neutral stance which means either your previous blocking stance or just neutral for peacekeepers and such.

The size of the two circles can be tweaked to make it feel just right.

This circle could be either on your character or the enemy you are locked onto,
I don't know which would feel right because most of the time you are going to be looking at your enemy and you need to look at your cursor to know when you are in the inner or outer circle. Even if this isn't the best way, I feel like these controls would make mouse and keyboard feel more responsive and not all over the place.

Here is a reference of how I imagine it, done in paint, don't judge.



The little blue dot would be your cursor, the whole thing can be transparent so you can still see even if it's in the way.

The outer circle can be separated into 3 pieces for the 3 block directions.