The catch window is too big. You shouldn't be able to catch a Pettis body kick with reaction so easily. When have you ever seen that irl? He kicked Henderson 4 times in a row to the body within a few seconds.
You shouldn't get a guaranteed rock later on in the fight due to chin depletion either. It's silly. You should either lengthen the window or reduce the damage on the counter for balance.
In terms of realism... Both should be changed. If a kick is caught (which is quite rare) then the fighter will go for a takedown for the most part. I can't recall a fighter catching a kick and throwing a perfectly accurate straight punch with a lot of power that rocks the opponent.
So in an ideal world the catching the kick window and the insta-rock counter would both be changed and something else could be found to balance it. That's an ideal world though. I'd also suggest making certain kickers' kicks much more difficult to catch (like Pettis and Barboza).