It's not that the different users' PCs have the problem, it simply depends where you go. If you go to the right places, you won't see any significant problems. Many settlements work fine, but some others are terrible. My group all have high end PCs. We all get the same problems in the same places to the point that the game is completely unplayable for a minute or so until it settles down, then it becomes acceptable, but not good. Other places we go work well for all in the group.
Also, it's not just the graphics that's borked. We have to spend a disproportionate amount of time logging and relogging to be able to see each other. In a group of three, one or two players can see only one other player, while one of the group can see all three. Three players jump on the same ship to go to a mission, only to find that one is back at the station as soon as the ship tries to jump. Mid flight, there are frequently messages saying somebody has disembarked when the two passengers can see that they're still on the ship, though the pilot sees them teleport to the ground, then back again. During a jump, one player will often end up in the blue tunnel of death. There are many other problems like that, which are really annoying. It's happened so often, that it has become part of the game. We know the consequences of each type of problem, so we know who has to log and whether to go all the way to desktop or only back to the menu.
I would say that in a two hour session, I have to log about 6 times, and I have to get the shuttle back to the station at least once after I got kicked out of the pilot's instance. Even when we're in the same instance and can see each other, it's pretty common when looting a base that one or two players can see an object (say optical lens), but it's invisible to the third player.
I don't mean this to be a general moaning situation, but it does show the faulty programming, which may be contributing to the frame rate issue. What happens within the graphics when an object or player is there but can't be seen? Is it spending a lot of resources repeatedly trying to render them without success? What else is missing that you wouldn't know because you can't see it?