Is this the part where you have to kill a specific named knight, also while a public event is going on, at the Skywatch? I got that part of the quest right after just doing that exact thing one of the few times I had someone else playing with me. I've tried it a couple more times alone, but just couldn't manage it without anyone else there. I read that you should use arc attacks to get through his shield. I'll try that next time.

Yep, back to the hallway! When I did this, if i recall correctly, enemies will span in the hallway (1 time) with you, so watch your back! I made sure my Titan super was charged and ready for them (Fist of Kill Absolutely Everything!). After that, I switched my sub-class to Defender (a.k.a. Bubble Boy) just to make sure I had a cushion of extra protection if I needed it. Good luck.

Bring a friend and drop the sword.