Just fixed another user computer with FPS problems, turns out that addon is not updated properly. 

    if you have FPS issue please check in the addons menu that the addon is at least 8.734, the installer might be installing to the wrong path. 

    1. Load the installer 
    2. Click on settings > click on auto detect path 
    3. Click on ok > click on reinstall

    try again, otherwise you will need to fix the install path manually
    it should be <your path>World of Warcraft_retail_

    if you’re still having FPS issue please post screenshot of your addons menu of that you have the latest version installed.