Its not that they don't see you matriculating at all, your taking what I'm saying to an extreme. They know you can get it done, and could succeed, but in the end the interview is still just part of the whole application. I agree that a GREAT interview can push you over the edge, and I think a bad or even mediocre interview can hurt you. I'm just saying that at the end of the day, the school wants its MCAT/GPA average to be maintained or to go up. Sure, Harvard interviews kids with a 30. At the same time, theres no pretending that those kids are on the same playing field as the kid with a 39. The 30 is going to need a KICKASS interview to get in. And many can deliver that because they are interesting, thoughtful, dynamic people.
I'm just a re-applicant who has been around this too long, and I'm admittedly too cynical about the process. To help the OP, just a couple things that have helped me were to do a mock interview with another physician who is familiar with admissions. This could be hard for some people, but really helped me - just find someone to do a mock interview. I also try to make sure I really sell to the adcom that I want to be at their school, and that its a top choice for because of X and Y reasons. Maybe they just don't think you're invested enough in the school. Even if you're not from North Carolina, never been there, don't have an opinion on the Duke/UNC game, don't really care about staying post-graduation, try and dig deep and convince them that their school is the best thing since sliced bread.