The numbers get your application read: e.g. no one is going to spend much time on an application that is 2.8 17 M.
The PS, secondary, ECs and performance in key courses get you an interview (Two applicants with gpa of 3.5, one with C+/B- in O-Chem, the other with A-/A gotta go with the later). The LOR can rule you out of an interview but don't otherwise help (unless they explain something very, very interesting about your background that you were too modest to mention).
You are asked to interview if you "look good" on paper. The interview can push you to the top of the heap or send you down to "reject" hell. At that point, numbers don't matter too much (unless you are borderline and being interviewed to see if you are so impressive in person that your substandard gpa due to problems as a freshman should be overlooked).
DO schools seem to be more forgiving of poor grades/poor scores. However, they also have a lower proportion of students who pass the boards on the first try or on the second in comparision to MD students. Using gpa and MCAT as a first cut may be a wise move on the part of allopathic schools.