Depends also how you hold the mouse, make sure its straight.. if its twisted and you move left-ish it might sometimes block more up than sideways for example. Reminds me that I should probably have written a hardware/software setup guide for cRPG that I never did..
Basically.. good stable connection, good fps, you can try turning off pre rendering of frames, quality mouse,
smooth clean mousepad, correct mouse sensitivity.. ++
Many things influence the performance and your human performance, the older your comp, the more you should probably tweak to make it run as smooth as possible. Smoothness and accurate controls are super important.