how about scav?
like one where players who would mess with others cannot use it in order to warp out just as a boss battle starts or right before, leaving others in a bit of a mess (i say this because i ended up with such trolls in other games before where they leave right before you pull and you get doomed.)
People could still just pull the boss - most don't care about dying, and it has no real penalty in this game anyway.If that happens, you boot them from your group, and don't invite them again. ;)