It's a great deal hey? I'd buy an adapter for my Xbone to use my Hori arcade stick if it was backwards compatible. Sadly Darkstalkers isn't yet, and Capcom haven't really gotten behind the BC program on the Xbone so I doubt it ever will be.
The Darksiders IP has been sadly neglected by modern Capcom. I'm presuming that they are intentionally holding the Darksiders titles back from the Xbox BC list in order to potentially re-release them at some unknown random date in the very distant future. It's a genuine shame. Modern Capcom is absolute cancer. They're such a terrible publisher. I put them in the same shit heap as Konami.
That said, a potential PC/Steam release would be a good last resort to preserve them, at least.