It would be harder, I agree. I don’t think they would be so much harder that it couldn’t be reasonably done though. They don’t have to do it all at once
It’s not that people can but don’t want to. There are people who do want to do group content but can’t because of no social circle. What I am suggesting would give people the opportunity to do so.
I could get behind a solo-mode with NPCs for Normal dungeons to see the story while you’re leveling. Heroic and up should still require actual players, imo.