Happened to me a lot when leveling DPS prior to 2.28. 1-in-4 instances isn't exaggerating the amount of occurrence. But is it just the first person leaving the dungeon gets penalty? Or anyone who leave the instance will get one? Because after the healer or tank leave, the DPS really have no choice but to leave the dungeon, but I haven't noticed that I "can't queue for dungeons" for another X amount of time or something along that line.