Each server is like 24 people, and you are randomly assigned a server every time you log in, as I understand it. If you pair up before hand, from the main menu social tab, you will log into the server your partner is on I think (though I have no idea what happens if that server is already full–it sends both of you to another one?). The fact that you are on a different server each time you play is why your camp sometimes isn’t set up and you have to redeploy it–someone is in your spot!
And yes, the limited nature and frequency of interactions with other players is either a good thing or a bad thing depending on who you ask. But in all the 100+ hours I put in before moving to some other stuff for a while, I think I had a mere handful of significant interactions with anyone.