Also, something not as technical and cool you can try would be to make a mouseover macro for the spell you want to pull with and keybind it to (scroll up) on your mousewheel.
This way your eyes will be fixated on the middle of the screen as you'll coordinating the mob distance from your cursor position. It'll make you faster than the other players who are trying to grab your mobs and you'll also be much less likely flag yourself mis-targeting
Theres also other benefits of using the mouse wheel to pull precisely, but like I said, I'm not gonna get technical. Take it from a PvPer.
Hope this helps - Cheers.