That's because the grid becomes too large. The mouse movement for every count is a big jump. Check out the thread I linked for a visual representation of how it works. You want the sensitivity in-game to be as low as possible and to achieve that without the sensitivity being too slow, you need to compensate by increasing the mouse DPI. To prevent the need for constant DPI switching, enable Raw Input and lower the WPS so you can just use the high DPI globally.
There will be a point where the sensitivity value will pixel skip no matter what, then there is the point where it will pixel skip at your given resolution. You also aren't limited by pixels as this isn't 2D mouse cursor movement. You are rotating a camera within a 3D world so you can rotate smaller than a pixel. Don't settle on just eliminating pixel skipping as you can improve it by so much more by doing at least half sensitivity, double DPI and changing WPS to 4/11 (50%).
The end goal is to achieve the lowest in-game sensitivity value that you can. However don't go overboard. You will be bottlenecked by your mouse as every mouse is different and can operate optimally up to a certain point. If you go past the point, you may suffer from smoothing, interpolation, acceleration, skipping, etc. If you are doing the global approach, you may encounter problems in other games because they can suffer from the same problems, like negative mouse acceleration if the sensitivity becomes too low.
Edited by Drimzi, 11 March 2017 - 10:09 PM.