Not sure if this was intentional, but at least the one I tried to tribute, Secure Phlogiston Ring had a zero tribute value. Seems like it should have a tribute value a bit below the raid drop ring.
Correct. As designed. Tradeskill items are often used as tribute mines, so on general principles, I don't spend the time to add tribute values (it is a separate step) to tradeskilled items. While Phlogiston does have a valuable rare component, I deemed the time better spent on other tasks.