Death is fine during dive, as long as they do not have weakness during teraflare. For the final Pain, our tank drag it into the neurolink and the dps will dps outside the neurolink until teraflare at 5s cast before we move in, it will die as teraflare hits. As long as it dies before or as Bahamut appear it will be fine. Once you can keep seeing Akh Morn, you are pretty close to clearing, divebomb phase is the only phase that too longer time to practice for my group, last phase was pretty easy.