It's been a while since I configuerd my sync tasks, but I believe there's a setting to import systems and structure in the AD sync task. That will copy the OU structure from AD to your system tree. Also enable the option to move systems from their current location to the location based on the AD sync. System tree sorting will be disabled on the imported systems if I'm correct.
If I were you, I would completely disable System Tree Sorting. I ran into sync problems the other day and was suggested to disable System Tree Sorting when using AD Sync by McAfee Support.
AD Sync based on OU: System Tree -> Select a Group -> Group Details -> Synchronization Type -> Active Directory -> etc