OK. In my comment, I was just trying to keep the discussion focused on non-academic diversity. I agree with what you say to a certain extent; I'm willing to consider other factors in admissions besides academic excellence. But I find it hard to believe that the quality of academics isn't negatively impacted to an unacceptable degree when a sizable fraction of the class (the OP claims > 10%) has much poorer scores (the OP claims roughly one standard deviation).

Also: Gauchos >> Banana Slugs