Perhaps if the repeatable quest for these materials gave a small amount of experience upon completion it would help in two (2) ways.
First, it would give them a purpose over the tiny amount of gold from selling the reward after you have a set or out leveled the gear.
Second, it would answer some of the desire to have a way to continue to progress your sire after completion of the daily quests.
I wouldn't suggest any large amount, something really small like 10 times the level of gear rewarded. So 100 for the first tier, 200 for the second etc. This wouldn't allow for a lot of progression, but it would give a sense of still being able to progress through playing.
An alternative would be to have a new quest which takes donation of these items for straight up Sire exp.