My guess is they're used for that pulse rifle which has yet to make an appearance. Though I've not heard anything about it since pre-launch. I'm assuming, like you, it's a raid exotic like ToM. It's probably a hard-mode raid gun though. That's the standard, I believe. VoG and Crota were that way. I never got to run KF, so I don't know if ToM was a hard-mode reward or not. So yeah ... No point in me collecting the stupid things. I'll be lucky to run the raid on normal.