World bosses award titan disc fragments when you are in a party or solo, but not in raid. But if you kill one while you are in a raid, you are locked out from looting them at all from the world boss. What people are doing is leaving the raid at the last moment. It phases you back to your phase, but you still get the disc fragments
I don’t think this is intended. I’m guessing a flag allowing the quest to be completed in a raid needs to be set.