I've been lvling samurai and just finished lvling monk only doing roulettes and beast tribe quests (not burning out on deep dungeon right before HoH) and ive been getting really good dps que times but that's because of the time I play at (mornings or late at night are perfect times for dps to que up) the issue with not a lot of tanks/healers in the que is because we haven't gotten a new job in that role in a while. I'm nearly done with Drk which will be my last tank job and once I finish samurai I'll be lvling Astro and that's my last healer. Give the players a new tank/healer (especially if it's a totally new take on how the role plays) and you have people back in the ques, u might not convert people from dps mains to a tank/healer but at least the current tanks/healers have something new to lvl and in turn gives dps faster que times.