Party members that make it clear through to the top and help damage the final boss should be able to rejoin their party in the same instance if they get dc’d. It’s stupid that you work hard to help your party and then get to the very end and can’t rejoin because of some freak internet issue.
I understand the reasoning if someone joins in at the bottom level, but we fought clear to the top and had the final boss heavily damaged. This is dumb.