A solo activity that can also be three manned will be made trivial. If it's intended for the masses to complete solo, then having the same challenge multiplayer will be pathetically easy. Unless theres a hardcore scaling for more individuals added, which would just feel more artificial. And if two separate missions like shattered throne were created, it would take away from one or the other. Neither would get the focus it deserves, and designs will be lackluster. Not saying your wrong, just saying there are downfalls to focusing on the single player experience in a game like destiny.