It really isn't the solution to the problem. The proper solution is just filtering people into random dungeons randomly, without letting them see the number of bosses defeated, and without letting them select whether they will deign to enter an in-progess run or not. You know, the way that every other dungeon finder in every other mmo works.

Either that or a penalty for the amount of withdraws within a certain time period, such as 3 minutes. 3 withdrawals over a period of an hour really doesn't address the in-progress fishing that I assume this was designed to solve. DPS withdrawing wasn't really the issue. Tanks fishing was. I know, because I was one of them.