Boneshatter in multiplayer HC

Im not sure if its hardcore mode issue or multiplayer issue, but boneshatter (warrior skill) is supposed to stun enemies that are primed for stun (which means 40% stun threshold for white enemies...) but while playing with my friends in hardcore mode this % was moved up ALOT, so white enemies could trigger stun at 60-70% stun threshold, while bosses were almost impossible to timed for stun since threshold has to be at ~95%(which normally is 80% when i solo), so basically they would be stunned by normal attacks of my teammates. I suppose this is bug because theres noway i can boneshatter in multiplayer this way, most of my enemies die before they get to stun trigger.