There should be other ways to obtain the Field notes.

[HeyMcFly]

I'm 6 days now on just Dyunbu my morale is effectively zero and I spend more time afk then trying to do anything , like the mettle returns in the southern front or so awful I feel as if I'm making no progress. It's so crushing I just want it to end Dyunbu will not give me mercy.

I finally got her notes from "For absent friends" I ran bozja for hours each day for more than a week, it wasn't quite 2 weeks- then it finally dropped for me
I only ran her skirmishes & ignored all others- that's how abysmal her drop is
It will eventually drop- just ignore all other skirmishes except hers & make sure that there isn't any ! icons for skirmishes, go pop those & let them fail, run back to dyunbu locations are- preferably near the crystals so you can teleport if need me