A good way to deal with this is simply by force people to complete a dungeon, this means, lets say a Picky Tank picks dutty roulette and gets "Brayflox Longstop" then he abandon for wathever reason, well the next time he picks Dutty roulete, the dutty roulete forces him to do that dungeon again until he completes it.

This way if the person DC'd or wathever other legit reason abandoned dungeon they dont get penalized with cool down timer, but if the tank ditched the group at porpouse then he gets penalized in the way that dutty roulette will always pick that last dungeon for him/her until finish it. worse case scenario these jerks stop using dutty roulete (wich is good), eitherway everyone happy. If you dont want play certain dungeon then dont pick dutty roulete, and just pick the dungeon you are willin to do. no one gets hurts with this method.