Overwriting it once or twice in the dungeon isn't terrible. If they overwrite it every time you put up Storm's Eye, point out that it's a loss of 60 potency every 6 sec combo, which is 10 potency per sec, which is 100 dps or more at Lv60. "You can do 100dps more if you let me do the debuff" usually gets them to stop, in my experience.