I played the Raven mission with two friends yesterday on ultimate badass mode and had some really strange things happen.
We decided to soften the Raven up a bit before the final battle by shooting it from cover while it was running around in the road outside the barrcade. This basically damages the Raven enough to shorten the loader battle by about 30 seconds, as long as you have one or two partners to keep the little xenos off while you're in the power loader. That trick has worked flawlessly the past few times we've tried it. This time things did not go quite as expected...
After we got through the gate and the battle got underway the Raven simply
vanished... And the little xenos just kept spawning endlessly. While it was fun blasting xenos like a shooting gallery, after several minutes we were running low on ammo and decided to reload the checkpoint. All three of us died almost instantly. Reloaded again and two of us who were keeping the little xenos off the loader's back went down, and could only watch via ghost vision while the loader finally killed the Raven and completed the mission. The little xenos stopped spawning except for one that kept dancing around behind the loader, apparently not doing any damage.
I played the same mission on ultimate badass the other day with Magnus and the Raven went down in under a minute with just two of us playing, almost too easy! The vanishing Raven must've been a rare glitch, as I've played that mission numerous times on every difficulty level, before and after the patch, and never had that happen before.
Anyway, since the patch it's nearly impossible to kill the Raven without help. The little xenos attack the power loader much more aggressively while the AI Marines fail to protect it enough to give you a fighting chance against the Raven. I hope this issue is addressed in a future patch because it obviously needs some adjustment.