I've played with a friend a few times and from what ive noticed the only way to join a multiplayer game is if everyone is in the lobby then the creator hits play. So chances are since you can't join a game in progress apparently, that's why you haven't seen anyone.

same here

always alone ....

The same is happening to me . It's confusing as it's written that other players of my level will be able to join my game when selecting public mode but nothing happens.

However, I notice that there is actually no option in the menu to join other public games. I guess that if there's no way to join random people's game, I can't expect random people to join mine .

Am I missing something?