Nobs are rare drops, just keep questing, even if completed. I find "To Catch a Thief" my best quest for nob drops.
Crystals after quest completion is even more rare, practically impossible. You'd get 10 nobs way, way, (can't stress enough), way before you'd get a crystal.
But i'm just nooblet, so don't mind me lol happy questing. Hope that gave you an answer.