A lot of DF parties can work. But very very often you end up with a deadweight that needs to be kicked for any hope of success for the rest of the party. However, if a person is kicked, multiple people often see it as a free ticket out of the party without penalty, and leave along with the kicked person. The party crumbles.

People on DF are often bad at recognizing whether or not a party can be made to work. That's why raiding on DF can be quite frustrating.
Kick a dead weight off the ship, and the rest of the party decides to go diving >.>