What monitor is it & what is your FPS when you see tearing? Different freesync monitors have different FPS / refresh rate ranges that freesync will work in. If your FPS goes lower or higher than the supported range on your freesync monitor you’ll still get tearing.
You should be able to find the range by looking up your monitors model number. To avoid going over that range you can use the FPS cap built into wow on the advanced graphics settings & if your going under the range, turn down your view distance if your CPU has a thread hitting 100%, SSAO & shadows if your GPU is maxing out. If your on Windows 10 you can use task manager to view CPU & GPU usage.
Or just use V-Sync, to be honest I don’t notice really a difference in input lag between V-Sync on & off, at least in wow anyways.