If they made it optional I would be fine with it. But it would be terrible if it was forced. I have lost track of the number of times somebody got disconnected during a raid or nightfall and had to join back in. Add in the fact everyone has that incredibly slow friend that is never ready to go, so we occasionally start down one person and they can join once they get it together. We have a solid team, if we want to do crota on hard with four or five people that should be our choice, sometimes a smaller team presents less opportunity for errors.