I loathe sitters. They're usually running around, grabbing materials going for the Strike without dying bounty. If I don't have that one I will do a suicide run to bring them forward. my bf usually rams them with the Sparrow to kill them. If I have the bounty I'll simply leave and try again in a few. I think that anyone who doesn't make it to the no spawn zone by the end sound not get credit for the strike. No bounty, no reward, etc... It solves the problem where people are not participating but active.