I want to say I also occasionally experience a very sluggish mouse. Its a rare thing, but when it happens, its impossible to aim and properly turn.
It cant be my hardware since my laptop and mouse are less than 2 months old.
In all instances it happened in the middle of pvp and it was instantly solved when I died. In all cases I didn't experience lag, only a sluggish mouse.
I tried to up my dpi to make it faster when it happened, but this changed nothing. Also unplugging and plugging mouse back in didn't help.
Edit: It happened today in the Tau-23 fight vs Hogosha