Something I’ve been thinking about regarding boss fights in general is that I think it’s a mistake to put Lords at the end of maps. Nurgloth is the first example of this, but also feels like the first true boss fight - I think they built a really fantastic boss concept, taking a lot of ideas from MMO boss fights (which are the best part of that genre of games, from a gameplay standpoint, I think).
But rather than stick boss fights onto the end of maps, I think they should be in their own mini-level. Shorter than most maps, but this allows them to be very challenging without being quite so punishing; there’s a big difference between having to do just the fight from the beginning and having to do the whole map from the start.
We could also get more involved, multi-phase boss fight, which I think might be an interesting concept. I’m mostly thinking about Vermintide here, but I think this also would apply to Darktide.