Maybe It will be some kind of long shot, but is it possible that you have this belt for very long time as well as you DH and belt itself is legacy item? That's the first thought that come to my mind after reading your post. It is possible that legacy items could reforge in different way.
It will be this. Hellcat Wasteguard got legendary affix later, and it wasn't retroactive (as with all legendaries in comparison to set bonuses).