It may make some difference depending on what class you queue with, I tend to get more lowbie dungeons on tank than healer. Also consider that not every player has access to every dungeon, while players are much more likely to have the lower tier dungeons unlocked regardless of level. I know it's frustrating to see the same dungeon over and over again (I got consecutive Tam Tara's weeks in a row), at the worst you could give yourself a break from roulettes. Roulette is going to keep placing you in the lowest common denominator, which unfortunately often ends up being level 20 or so dungeons.