I’m not sure whether I’ve actually missed a mission or environmental story-telling, or experienced it but took away something different from it. Could you elaborate (perhaps using spoiler tags or PM as needed)?
I was very, very wary of it. It’s certainly a change in tone. Between having regular quest givers in hideouts that wanted orange juice, and suitcases to loot, the DLC felt weirdly like “Dead Island in the snow.”
It kinda works, but yeah, change in tone. That said, it’s kinda nice that they kept the one style in the main game so there’s a clear separation. But something had gotta give. It didn’t have to be meeting quest givers, but something had to happen.
It could’ve been “You make contact on the radio, you build trust, you finally go there to meet them, but when you arrive, they’re all dead: Your communications allowed the machines to triangulate their position.”
(Yours as well, but you were in motion and alone, so the other survivors were the more attractive target.) The weapons you find on their corpses are your quest reward, but they’re a cold comfort. (This latter bit is of course already the case for weapon you take off army people; the difference here is that you first build a relationship with the people so it matters when they’re gone.)
Heck, even if you never meet the people, there could’ve been something more personal: “Strengths in Numbers” could have been such a mission. Right now, you hear the message, but by the time you get there, people are gone, and that’s it.
That could have been multiple hops, learning more about these people at every step, bonding with the in their absence.
For extra credit, you could’ve found pictures of them, so you could identify them in the final mission (keeping things a bit vague here, because, spoilers), as a kinda brick joke.
(Yes, that would’ve been a somewhat clichéd and heavy-handed ending, but our genre here is '80s scifi/action.)
etc.
And this is just random stuff I’m pulling out of my butt at 5am, making it up as I go. The main game should have been able to beat that twenty times over. 
(The DLC on the other hand had one one hop story, Father and Son, that I nonetheless liked, and it wasn’t because the questgiver was alive, it was because of the environmental story-telling at the destination.)
Spoilers
It’s a bit of a bitter-sweet ending. The estranged father you’re looking for is dead, but he didn’t die alone, and he spent his last time in his son’s room, and passed looking surprisingly peaceful. I found that rather touching for some reason.
tl;dr The story-telling didn’t necessarily need alive quest givers, but it was very weak and needed to step up its game somehow.
