Without looking at this too close, the first thought that comes to mind is that it's not a good idea to use pitchers nearing the end of their careers or minor league guys who haven't hit the majors for the simple reason that these guys could have plenty of non TJS reasons as to why they are no longer in the majors. Plenty of prospects (even highly thought of ones) never get there for various reasons, and plenty of vets fall off a cliff in their 30s. I would think you'd need to normalize those numbers based on success/failure of non TJS players in the same categories... that isn't easy to do.
As for Aiken at 6, it's all risk reward. If there's reason to think the risk is a bit higher for Aiken due to some medical reason, I probably let him slide. If this is a standard TJS type deal, I'd have a hard time not taking him, especially in a weaker class.