Either make it 0%, perhaps that maybe a little radical....
Or, change the code that spawns new dungeons at 60ish people to be side based.
So the new dungeon would hold 20 clan, 20 Omni and 20 Neutrals (is there that many?). Not like it takes more than 6 people to kill tar.
The 21st clan/omni/neut would spawn a second dungeon for example but other sides would still zone in to dungeon 1 until they hit their 20 limit and then zone in to dungeon 2.
That way we can have a fight and neutrals can form tactical alliances with one side or the other for a share of loot, or go for it themselves. Be nice if warps were stopped in to full playfields too.