I don't agree with the whole 'the developer's made it like this so that's why 'we're' like this' argument.

The developers didn't decide how you should behave towards others whether it's your first time playing through the content or hundredth time. I can definitely understand the frustration that experienced players might have, especially if you're trying to run through content quickly, but if you want constant exclusivity in your party, you're going to have to do something exclusive to the Duty Finder, making your own group with your own intentions for example.