I have to admit, I dont run focilize even though it's one of the best CCs in game because I want people to not be CC immune when I leap, and roots right now can be almost as good with buggy immunity there and short recourse time
Leap causes an impact that sends enemies off their feet... flavor wise it has to be a knock back. A stun wouldn't even make sense. Don't balance a game around bugs or lag... fix the bugs and lag.