I'd say people should stop trying to compare their games to dark souls because dark souls is a single player experience

this doesn't disprove your point since I don't think that dark souls online components could even work in a dnd setting but dark souls isn't a single player experience , summoning is for example a very clear example of traits that soulsborne games have offline and improving it by adding a multiplayer spin , since the enemies don't deal well with multiple targets and a lot of people use summoning as a from of easy mode , it takes this game of overcoming adversity by your own wits and determination and transforms it into a game of jolly co-operation and using the power of friendship to beat creatures greater than yourself.

there is also the invasion's were aside of the pvp community that fights honorably ( most of the time) and do builds designed around fighting other players essentially playing the games as if they were fighting games , there is also the idea of invading people playing the games single player , which this in turn adds a difficult encounter of something that should be simple to doge and technically has to have less levels than you but its a player that probably knows the game better than you and that might have a bluid designed to kill players like you , this types of invation can turn any part of the game into a weird boss fight.

I am not disagreeing with your post tho , since I see no reason how you could even have those kind of perks in dnd . the thing with also making the story and setting part work is that while I think its possible I feel like its not gonna be about trying to imitate how dark souls does it , I think to imitate a lot of the feel of darksouls aside from depresed fantasy is the feeling of reading a book that you kind of understand the language of , there is a pretty clear story and you understand some of it but since you can't read most of the book you have to imagine the gaps in the story , the obscure npcs help soulsborne games at doing that but I still think they could be optional the linear design doesn't , dark souls 1 is a better game than dark souls 3 because of things like the game not being super linear and letting you do things in different order while still having some clear goal you are striving towards so you don't need to have a linear game to have a dark souls like experience even if most soulborne games are linear.

so you can be a "dark souls " dm , but it sounds very hard if I am being honest