Amidst several server restarts tonight, I waited ~3 hours for Astorius, ~2 hours for Simone, ~1 hour for both Klinfran and Solenor. I patrolled the supposed spawn area for that amount of time for each demon, and I did not once see any of them spawn. I'm assuming the quest mobs are somehow currently bugged with all of the changes the server is going through. I've submitted an in-game ticket, but my last ticket went unanswered for three weeks before I clicked it off. As soon as I'm finished posting this, I am going to submit the bug to the bugtracker.
My best guess is that with the core swap and the changes, they either reverted the demons to their original ~4 hour respawn rate, or they bugged them completely to the point where they will not spawn.