I have done multiple capstones where we complete 2 of 3 bosses and the group fizles for 1 reason or another, spending 15 minutes in a group and getting absolutely nothing sucks. The last run I was in was smashing it, we had 25% left on the final boss with 4 minutes to go and everyone just left out of nowhere. On top of having no idea why, I get nothing for my time and effort and it feels really bad.