Harriet Miers is not a diversity appointment any more than those women would be. Now you may think that Luttig would be better, but the President disagreed. We don't know why he disagreed. Maybe Luttig didn't want to go through the process, maybe something came up in the vetting process, maybe the President just felt more sure of Miers judicial philosophy. You have no proof that Miers was chosen simply because she was a woman, any more than you can prove that John Roberts was chosen because he is a Catholic.
Oh really? I was born at night but it wasn't LAST night.
Remember Laura coming out and stating she strongly preferred the next nominee to be a woman?
As PC as this Administration is, it is a good bet that that was precisely the calculus used.