There's been a few cases where there are only 3-4 event raids open. Most prefer to jump into a raid that is fairly recently spawned, but this is much harder with this event. Once say 25-30 toons are in, most don't want to join because the OS phases are already done.
This could be mitigated with more raids spawned early in events (like now). The OS phases also seem much too short and the boss phase too long. I think so far I've only had two instances where I've actually finished a 6e OS round before the phase is over (it's not killing speed, because in several I've still finished the raid top).