For the love of anything, please check the rates of abundant, bountiful and rich missions for fabric versus metals. The ones for fabric come up 2 to 3 times more than the metal ones do. And that is at all levels.
Also check the drop rates for the purple gems in Treasure Hunting. I don't know how many times I run the Rich level 3 gemstone missions and come back with nothing but the blue stones. I realize there is supposed to be randomness to all of these, but good lord. Some of the drop rates are incredibly low!