If you want to instance, you really want to be going in with 5 toons. If you really want to do a 4 box, you'll probably be looking at bringing one other whenever you run something. In the worst case scenario, it'll be a random person on your server. (a pug) In the best case, it'll be a friend or guildmate. Either way, you'll want to try to build a team that can work together with a random element.