If they have been doing this for three to four years shouldn't they be better at it?
At some point you need to decide if Mayo is actually a third baseman. Folks gave Dan grief for keeping Mountcastle at Short for too long.
All the stuff you are talking about is great if the player can do it.
But I question how good it is when you have a bunch of guys that had questions on defense when they were drafted and those questions are still present years later.