Interviews, by definition, are not standardized tests. The more you think like they are standardized tests that should be done objectively, the more useless agony you're taking on yourself. It's never going to happen. It can't.

On the spectrum of human interactions, interviews are closer to a date, than they are to an exam. If you make a connection with your interviewer during that hour, (via whatever topic it is), they will go at lengths to hire you. Yes, you're expected to solve the given technical problem reasonably well, but beyond that, you have to leave it to "chance" and "pray" that you get a good panel.

That's how it SHOULD also work. Because YOU are also interviewing them at the same time. If you don't get inspired with the interviewers, you should also not join that company. i.e. you're also looking for a human connection.

I train for technical interviews for a living, at our exclusive bootcamp for interview prep: http://InterviewKickstart.com . Our entire theory is based on this premise i.e. that interviews are not a standardized exam; they cannot be gamed. All you can do is practice technical stuff really really well. In the end, who gets hired is not in your hands. And that's okay.