There needs to be a minimum 10 level difference in the dungeons you get for leveling roulette. I've taken the 30min penalty three times in a row now because as a level 66 tank, I've gotten Bardam's Mettle all three times I've queued for leveling roulette. The xp bonus you get at the end is not worth the daily. It needs to be restricted to lower level dungeons, like if you're level 65, it should only unlock dungeons from level 55 down so it doesn't feel like you're burning your leveling daily for weak returns on the bonus.