Eventually I have an "awesome" (Hey, wait, when have ever been my ideas awesome? If I'm a noob...) idea:

Tell your friends to use tank or healer, and use tank or healer, then DPS will have faster queues and... WHO KNOWS!.. MAybe....Even... a bonus in roulette... The other day I saw bonus for DPS in Main Scenario Roulette, I wanted to take a screenshot because nobody would believe me, but was lazy, so wether you wanna trust me or not depends of aetherial forces.