i have a g5 and getting an average of around 450Hz on the mouse tracking. i also dont have the cpl mouse fix thing. i think that is the problem.
I have never had the problem your using, and i prefur this g5 10X over the 518.. i havent tryed the $100+ Razer but it has bad reviews b/c of the buttons breaking from to much clicking.
whatever you deside, i’ll buy the g5 since it sucks so much. 
but its not the mouse.