My soul crys as I read this
As the player responsible for at least 99% of open world PvP and sieges I would contend that they are reasonably attended. In fact if it weren't for Rex Nex and social rejects intentionally imbalancing the odds things would be way cooler.
80% of my sieges this year 10ish have had 50+ attendees..... most of my Boris brawls have had 40+