Eso and planet side are that big. There are ways to design around that, but a dedicated server is required. You couldn't host in on a p2p network which is what destiny uses. What it comes down to is there is no persistent world that you can load into a meet up with players outside of your fireteam, whether it is instance based or one giant world. Even if I could run/fly from the earth to every other plant if I can't load into a specific zone and meet with people it's not an open world it's just a spliced together closed (meaning hosted) instance zone.