Ever since vanilla I've been using an addon called Gymnast Tooltip. What it does (the way I'm using it) is to move the unit frame / tooltip of the mouseover target so that it is displayed right under the mouse pointer instead of in the bottom right corner of the screen.
This addon has not been updated in years, but right up until I updated to 4.0.1 it has been working flawlessly. Right now I can't get it to work anymore. The '/gtanchor mouse' command is simply not recognized.
Any ideas how I can get this addon to work, or if there are other addons that provides this feature that still works?