If you're doing the bounty hunting massacre missions just make sure you're going to systems with either a compromised nav beacon or a Haz Rez site, and then do your missions in those areas. You can just sit in them and the pirates will eventually fly up to you. If you're going to the mission target signal sources then you need to have just one of your wing go to it, and then everyone nav lock that wingmate so when they drop out they'll pull the rest of the wing into the same instance. Otherwise I think you'll all end up seeing and going to different signal sources.