Some notes on why self-referential design is a problem, and why usability testing is important.
The team will have changes to the product design in mind: enhancements or new features.
There will be overlap in the design changes desired among the team members.
Usability testing will confirm that some of the changes suggested by the team are necessary.
There will likely be many unanticipated discoveries: completely new issues, designs thought well-vetted present difficulties for users, and those thought of as clunky prove to be intuitive or usable. This is why we test!
Takeaway: Self-referential design will cause you to fix problems that aren't there, and miss real problems that would have been discovered through usability testing.