I have ran into this problem since patch 3.1. It seems that all roulettes are affected by this bug. I say bug, because I've tested this theory. On any roulette the class count goes from 1/1 for a tank or healer,1/4 for a DPS to 0/1 and 0/4 respectively.I thought there was something wrong with the DF algorithm so I stayed in the queue while it read 0/1 for almost 2 hours before I gave up and queued for specific dungeons and got in one under 30 seconds as a healer and under 3 minutes as a DPS. I have done this with all levels of dungeons/roulettes leveling, main scenario, level 50 and level 60 and this only happens when I'm queued for a roulette.