I’m more or less in the same boat, but some of those mastery requirements have just made me say: “Screw it” just to get them done.
As for this glitch, in the Broken Hill Murder Pits there is a rectangular arena, you’ll recognise it when you spawn, as you typically spawn facing a downwards ramp, and a set of what looks like conveyer belts. What you want to do is immediately turn around and jetpack climb the wall roughly in the corner directly behind you and up to the next level. After that just run forwards to the back of the upper level and climb up to the highest point at the back of the map. Once you’re there the AI will seem to forget that you exist. You can pretty much just watch the bots all fight each other at that point and plant the Respawn Beacon the second the rest of your team dies and not have to worry about anything.