It probably could work. Destiny does this on consoles and it works. And OW has more complex abilities and mechanics. So that'd allow for more interesting engagements but it wouldn't work because there isn't a point to it. We don't get gear or anything in this game. If they do this, it'd have to be in the form of a campaign mode. Where the 'Dungeon' is actually a big map where we have some sort of mission or objective, and it also gives us background story on the characters and world. That could work but I don't see it happening any time soon.