Lylirra hinted today that Fiery Brimstones may receive a new use in the future. Although no details were given, the hype has already started to affect the price of Brimstones. At the time of this posting the price is at 85,000 gold per Brimstone, compared to an average of 10,000 for the past week.
We've definitely discussed the possibility of allowing Hellfire Rings to salvage into component pieces, and have debated your feedback quite heavily as a part of that process. While we understand why players would like Hellfire Rings to salvage into demonic organs (or even Keywarden keys), we don't think that's the right way to go right now since it would essentially let you skip some encounters completely. It's something we may revisit in the future, though, once the event has been around for a longer period of time.
We do agree with you, however, that the rings should be able to salvage into Brimstones, in addition to Magic and Rare crafting materials. The reason we didn't go with Brimstones originally was that we wanted to avoid the situation where you could always get that particular mat from a single item, over and over. The idea doesn't really sync up with our design philosophy, and the market is pretty saturated with Brimstones as-is. Even so, we know that it can feel cheap to not have a chance to get a Legendary material from a Legendary item, and we don't feel like our original reasons continue to hold up in light of the feedback you've provided us.
Since I know this will get brought up: We're also exploring ways to improve the worth of Brimstones, as well as crafting in general. We feel like the system itself could use some revamping, but we're not yet at a point where we can discuss what kind of changes we're considering. We haven't ruled out the possibility of introducing new recipes at some point in the future, though, or introducing other ways for players to put their crafting materials to good use.