Possibly already mentioned but if you die whilst above or on the railing on the far left walkway during the boss fight in Dust Palace (the one that connects the main building to the landing pad) you can't be revived and have to let your timer run down and revive yourself. Well, you can be revived but you instantly die again... Happened by pure chance when I was trying to run away from a ton of enemies that had spawned. Tested it with my mate and the same happened to him so there's definitely a bug. I should probably have recorded it and sent it to Bungie cos I'm not sure my description is clear.