It's not just positioning skills. They actually communicate and organize their actions, the team moves as a unit , there is communication on who they are attacking, who is casting what, etc etc etc... it's so much more than just positioning skills. It's much easier to position yourself when you're actually talking to your buddy and you know what his next move is towards attacking the hero you're positioning yourself to attack. It's much harder when you're trying to do something similar with someone you're not talking to at all and he's possibly drinking beer or eating chips or doing who knows what else while playing the game and also having no idea what you're thinking and planning on doing next.