Personally I think pass rate says more about the school than anything else. Schools should be preparing people to pass. How good they do above that is based on the hours, sweat and tears they individually put in. If you're getting through the first 2 yrs of school and not passing the COMLEX, then something is most likely wrong with the curriculum, because it should have prepared you to do at least that.
Also, let's not pretend that pass rates and board averages aren't correlated. I mean a pass is literally based on a score cutoff, right? You have to score above a certain amount, and if a population has a better pass rate most likely they will probably, but not necessarily, have higher board scores, because less people are pulling down the average. Again, its not always the case, but it's certainly correlated.
In any case, none of this matters. As a DO applicant, you can't predict how well you're going to do on boards, but you know passing boards will get you a residency spot somewhere. If you're school can't practically guarantee that happening, then it's doing you a disservice.