Jeez. How do you come up with such an idea and why? If 2 people do a quest together they usually do the same amount of work. Along with the water changes from A21 and magazines this is another step into kinda forcing people to go solo in a MP game.
If this is just to slow down progression what will happen is that many people will spam quests like crazy solo until T6 wich defeats the slowing down again. They nerfed trader rewards so quests aren´t as OP anymore and people don´t just spam them but at the same time they give us another reason to spam them. Nice.
I hope that is just a bug or something.