Heroes use it like they do Reversal of Fortune - you need to be taking damage before they'll remove DP from you.
Please change it so that they'll remove DP regardless of whether or not you're getting attacked. It'd be even better if they use it as often as possible (aka. make it the highest priority skill on the bar).
It'd be nice if heroes would spam the skill on recharge on any party member with DP. Although the difference wouldn't be that noticable in my opinion while you're fighting Dhuum.