If you let people smash there heads into the wall until they win, they will. Hard or not it's bound to take a few days until someone gets lucky enough to win.

I'm not saying we should enforce cool-downs but really there should be some limitation to just "Oh shit let's retry it!" Make people run through a small area even to discourage mass re-do's. At least you have to obtain your loot item after a win so that is one thing and a good thing if you ask me.