Do the Diamondbacks have one of the oldest AAA teams in baseball?
Pretty much, for a lot of good reasons:
1) The PCL is such a hitter's league it's almost a waste to form young everyday talent there.
2) The D-Backs are a team of mismatched parts as it is. They signed a lot of veterans and long-shots to the AAA team as a way to create depth without having to push the young guys up too quickly.
3) The D-Backs farm system is still another year or two away from being rebuilt. They don't have a lot of guys who could make an argument they belong there. The best everyday prospects are still very young.
I was a Dodgers fan back in the 80s and they did this often with Albuquerque. In fact the entire farm system was loaded with veterans. They rarely wasted a contract on a wash out. The idea was to create a sense of professionalism from the very start. It definitely helped in the early 80s, but I think their scouting department started to fall apart and by the late 80s the farm system was total garbage (save for a few real gems) after about a 25-year run as perhaps the model farm system.