That is definitely a bug then. Thanks!
How nice mastercrafted items are is directly related to how easy it is to get rares. If rare harvests can be obtained like commons, then mastercrafted items will have to have stats no better than commons. If you want mastercrafted items to be super nice, then rare harvests have to be quite rare also. (Exactly in the same way that raid gear is awesome BECAUSE it's so hard to obtain. If it were easier to obtain, it would have to be less awesome.) We always try to find a line between the two extremes, but desirability of mastercrafted gear and ease of obtaining it are always directly related - change one and the other has to change too, or the game balance would be broken.
