As my gladiators got higher level I noticed an increase in getting K.O.-d. Mostly against theatrics wich is not a surprise. How ever it is not that often.
If I would try to defend against it I would wear a heavier helmet, or set my strategy to defend head. At the moment it is not that annoying for me. Maybe at Primus and Blood Goods level. I guess when you get chain K.O-d one day it is frustrating and it can cause confirmation bias that this skill is too overpowered. On the other side, how many matches do these K.O. theathrics win with the skill (match that they would not have won)? I think it is not as reliable as one might think.