I think they should make it so that someone can not get another random dungeon, untill they finished the one that they received the first time.

A example Player A gets Copperbell Mines, Player A does not want to do this dungeons and goes offline to fake d/c or just leaves. Player A clicks on random duty after the penality is over and instead of getting a random dungeon, Player A gets Copperbell Mine again. Player A will keep getting Copperbell Mines, untill he finished them.

This way there is no extra pointless way punishment and Player A knows that he has to finish this dungeon sooner or later, so he grind his teeth and do it.