Bonus means nothing to me. I know many people who were carried through T5 and couldn't help a cleared party with 1 or 2 bonus people because they couldn't pass conflag phase. Or got carried through Mog/Levi ex and keep failing pretty hard at Ramuh's first phase.

I find carried people being more of a dead weight than any bonus first timer because they didn't really beat the previous content and they shouldn't be there. And you never know when you have carried players in your party.