I think there needs to be a method to upgrade these materials.
Since the release of IC (on PS4) the cost of the legendary upgrade materials has increased by nearly 300% on the guild traders and the price for the lower quality (greens, blues and purples) have dropped massively.
This is mainly because of the amount of farming required to collect enough materials to craft v16 gear which has created an abundance of green, blue and purple item drops. As high tier crafting nodes were not included in the expansion there is less refining, so the only place to get legendary upgrade materials is from daily crafting writs and hirelings (unless you go back to lower content areas and farm material nodes).
There should be a method to upgrade or exchange these lower tier materials for higher ones. For example you could exchange 4 Honing Stones for 1 Dwarven Oil; 4 Dwarven Oils for 1 Grain Solvent; and 4 Grain Solvent for 1 Tempering Alloy.
I think this would help in the long run as they seem to be releasing content at a much faster rate, causing more gear upgrades.
What do you think?