Suggesting to make 3 new jewels giving elemental buff damage % and 1 jewel damage resistance. These could be crafted with the 5 current underused jewels (lightning, water, diamond, chaos, nature)

Example
Noble lightning nature and chaos are all combined to give a % shadow elemental damage.

Noble lightning nature and diamond are combined to give a % resistance to shadow damage.

Just a quick thought on something to give these jewels a purpose. I'm sure others could expand on this idea. I haven't thought of a % or full implementation of this idea just something that came to mind.