Look at it thi way: a player joining a queue and subsequently withdrawing is equivalent to that player never having joined the queue in the first place. By extension, 20 minutes of repeated withdraws is equivalent to staring at the Duty Status window showing 5/6 tanks for 20 minutes. The progress vultures aren't actively impeding your abililty to form a group, since the spot they would be filling is empty anyway; the only thing they're changing is your perception of the process.