Unfortunately, rumors and postings on blogs are often the best barometer you have for a firm or school. I haven't gone through OCI at a Tier-II school with bad grades, but I'm assuming that it's tough down there because I've heard it's tough on these forums and other sites, and I met Tier-II students who told me it's tough unless you're a top student.
So that's life. Either work at Cravath despite the rumors or don't.