I've determined with playing with other actual people that you have to have a strong enough internet signal. I was on my home wifi and that wasn't strong enough. I went to my workplace and connected to my wifi there (which is a business class wifi and I was the only one there at the time) and I was able to join others and get people to join me. Unfortunately the Switch dock doesn't have an Ethernet port, but you need a very strong wifi to get an actual connection strong enough to participate in MP. I suppose if you have Xfinity's highest home internet package you probably could do it, but like 25 mbps, 40 mbps, I'm not sure that will cut it it seems... And yes, the NPCs that join the 5 star raids are 100% of the problem with completing them...