Thanks for posting. This topic has always fascinated me. I wrote a paper about it in law school, and at least at that time (2006), Scalia had the worst record for diverse hiring. When he was taken to task on it by a reporter, he was basically like, "well, there just aren't women and minorities in my pool." Which was because his pool was essentially Yale grads who clerked from Alex Kosinzki. He didn't see anything wrong with the fact that perhaps there was something wrong with relying on a pool that only generated one type of applicant. It's honestly no surprise he's so nasty and ideologically rigid given his commitment to only surrounding himself with people who fit a very, very specific mold.
Clarence Thomas actually has a track record of having one of the most diverse group of clerks. Clarence Thomas also does not rely on the feeder pool at all, and goes around it. He also tends to have the fewest number of clerks from law schools known for producing particularly academic lawyers (Yale and Columbia, really) and tends to go lower in law school rankings for his clerks. But in his case, his opinions are often notable for being so poorly reasoned that I've questioned whether he goes lower in rankings not for diversity in thought, but because he's self-conscious about his own intelligence and prefers to find long shot candidates who are just grateful to be there.