Ive been messing with guard sensitivity and mouse smoothing trying to find something that isn't so completely imprecise... I had this on lock in Open beta, but the same settings no longer help, not sure why.
Anyone else using mouse that has found a new magic combo?
Problems
1) I guard but it reacts too slowly
2) I guard but then my pet rat farts and it changes guard.
Yeah I was thought I didn't react in time but then I realized that it's the sensitivity is too low and sometime when I clicked light or heavy it changed the direction. Sensitivity 5 is good for me. Also I think your mouse's DPI might affect that. If the lowest sensitivity doesn't help then maybe you should try that.
Also remember that left and right in this game isn't perfect horizontal. It's more like South-West or South-East. Which will further limit the input error.