I'm amazed they haven't did anything to address this yet. The jewelry writs are completely useless because the value to do them isn't worth the reward.
When you decon rings/necklaces, the chance should be to get the plating versus the grain.
However, another option is to increase the rates at which you get the grains.
As of now though it's useless and too expensive to do the writs, so unless you guys change something you may as well take out the jewelry crafting writs.