I dont wanna be a hater but, cat is op yes but it is also not so op. Cat get more damage when they get hit so if you are holding a stone sword you MIGHT able to kill a cat which i got killed many times. Or you know how to strafe a person who using speed 2. Cat speed also bad, sometimes you get lagback whenever you run which make it suck. And about wither 2 for 8 seconds isnt too op because it only make you lose 2-3 hearts and you can also run too if the person who using cat dont know how to control their speed. About the launch, yes it's op because it can launch you up to the sky high or into the void. But sometimes you get lagback and instead of getting kb, you standing where you get launch so it also isnt too op. You can also died really fast if you 2v1 [ Cat vs 2 any kits ]. And also like CraftedCraft said, farming with Cat kit is like you farming a Killaura team.
Lets say your a acro and a cat with speed 2 comes do you think that extra damage is gonna counter the speed ?ofc not and 2-3 hearts means alot cause most of the time your not gonna have full hp... And cats can easily run away from 2v1 or out strafe people