Which area do you mean by the brig?

: Nobody back when I cared seem to do these kill everyone soeedruns.

As far as I know, they still don't, which I think is a pity. To me it's like the speed running community is a bit too obsessed with the absolutism of simply getting through a level as fast as possible, i.e. doing unrestricted speed runs. I've known people who wouldn't even call mine a speed run. They'll only use that term for unrestricted runs. They see that as the real stuff, whereas it's only one variety. I've only encountered a couple of folk who took an active interest in the kill 'em all idea, but I don't think any videos ever materialized. One guy had aimed to beat my 8:29 for POA last time I tried to promote interest, but I think the covies may've got the better of him as I never heard about that again.

: I used Pistol and AR plus grenades, I just couldn't
: kill the groups fast enough and I needed to retreat behind cover.

I know the feeling of course. Your shield can go down in a flash on Legendary. Is pistol & AR your favoured combo, or were you just using it to compare with my run?

: My capture card is broken enough that I would never upload a video, though
: I guess I could do it on PC and upload from there.

I've often found PC footage hard to watch because usually the player rotates to new directions in the blink of an eye. That makes things very jerky and even disorienting compared to the smoother rotation you get with Xbox footage. I'm not used to it. But if you ever release any runs, please make sure I know about them, and I can potentially add to my page of run links.