Three things I had to do to get this working, and one thing you have to do every time you go accept quests:

1) Make sure all 4 PCs mouse movement speed slider in Windows control panel is set the same AND make sure acceleration is turned OFF.

2) Set your alt PCs are all set to the same resolution and the WoW clients are set to the same resolution as well (can be different from the desktop but must be same setting in WoW options).

3) Not so obvious: make sure your UI Scale option in WoW is set to _exactly_ the same values. Easiest way is to go find the value in your WTF\config.wtf file and edit it there while out of game.

4) Then, once you have the above set up, every time you wake the mice up to accept quests or fly somewhere or whatever, just "zero" the mice by dragging the cursor up to the top left corner.


The above worked like a charm for me, with #3 above being a non-obvious problem I ran into. You _cannot_ adjust it correctly using the in-game slider unless you slide it all the way to the max or min setting.