Caleb Durbin was in the system during spring training, so not exactly random. Plus, he was a leading candidate for 3B (as much maligned as that decision was).
Miz's upside was also known, but maybe that is earlier than most expected.
Priester and Vaughn have to be the surprises of the season. Even after trading for them, people wouldn't have thought they would've had much impact on the season other than keeping a spot warm for someone to return from injury.