There were some improvements made to better support Dual-Core CPUs.
This will require adding the following CVAR to the Config.wtf file located within the WTF folder inside the World of Warcraft install folder:
- set timingMethod "1"
You can also type this command in-game, but will require a restart to save the changes:
- /console timingmethod 1
If this does not help try setting the value to 0.
timingmethod 1 is generally for systems where the cores do not synchronize.
You might run into issues like your framerate caps at 64 instead of your vsync value.
timingmethod 2 is a higher resolution timing method and you won't hit the cap with that.