Last night, a couple friends and myself fought our way through slaughterstar to red rain and blue fire with the hope of farming rowans call. We killed each of them and then killed ourselves by jumping off the edge, leaving quite a few enemies still alive so as not to finish the mission. Upon respawning, we fought our way through to wave 5 again and the mission completed without even spawning red rain or blue fire again. What did we do wrong? Do you literally have to play all 5 rounds just to get a single shot at rowans drop?