I think that it is really difficult to rank these things, and it generally varies by school, and everything sort of combines to make the "whole package". I would say that if you have stellar GPA and MCAT (>3.9, 37), or some really amazing/unique ECs, then they may be enough to make the secondaries not very important.
Otherwise, schools generally use secondaries to sort through all of the applicants that have similar applications. They will have a stack of people with a 3.8/35/standard ECs, and even though those are really good stats, they aren't going to interview all of them. They choose which ones based on PS and secondary answers.
TL/DR: Don't give in to temptation to blow off your secondaries. Although they seem ridiculous, comparatively unimportant, and like a major time suck, they can make the difference between getting and not getting an interview.