Santo was one of the best third basemen to ever play the game. Defensively, I think Brooks Robinson and Pie Traynor were the only ones who were better and he clobbers them both on offensive statistics, even though most of his career was in a pitcher's era.
Ditto for Bert Blyleven-- a very good pitcher, but not up to the Hall of Fame standards compared to the others which you mention. Still, in Bert's case, I think longevity does count for something and he'll get in just as Tommy John earned his way in for the same reason.
Agree with you completely on Ron Santo. Hopefully the Veteran’s Committee will get off their butts and get him in while he’s still alive. And they should get Gil Hodges in, too, while they’re at it.