So KO is in the game because of videos in youtube?
The skill essentially does the same thing as a skill that deals infinitely large amount of damage to the hit gladiator (always more than his/her maximum health), only without a chance to kill him/her. I suppose if it was formulated that way, you wouldn't like it. Or would you?
In my opinion there should be no "instant win" skills like KO (and no skills without a proper counter like Last Stand) because they are no-brainers and make the fights more boring. It doesn't really take a genius to train Called Shot and KO and aim for the head all the time - this guarantees at least 15-20% success rate no matter how good your gladiator is otherwise. KO can be kept in the game without the respective Theatrics skill though because it triggers rarely and doesn't look like a cheat.