The ONLY section I've found worth my time on Q-Bank is the dental anatomy section. I'm still believing that the other sections were taken directly from the USMLE Q-Bank (whereas the dental anatomy was obviously created for us).
If you can get 60% on those other sections then I think you'll do really well on the NBDE, but some of those questions are so far out there that they contain material I've never even heard of (especially Micro/Path). The Physiology questions are NOTHING like past NBDE questions, and the Anatomy questions are also from another planet.
Just my 2 cents.