You would be far better off turning file sync off and using folder redirection to point the My Documents folder to shared drive that holds the user home directories. The problem with this is if they are laptop users as well and require to work away from the network they won't have files synchronized. To get around this I created seperate laptop accounts for each user and pointed the My Documents to the same user home folder for their netwok logon. The laptops are in a seperate OU that has file sync enabled.
To reset the files on a client that is syncing other users documents the only way I a have found for rectifying this is to log onto the machine as local admin browse to the windows folder, there is a folder called CSC which holds all the cached files but to see this you must go to tools folder options view and uncheck Hide Protected Operating Files. Once done delete all files and folders in the CSC folder and reboot.