I've played a few games where Barbatos has killed a AI Civ either right after he first spawns, or pretty early in the game. I've also played a game where I did not see him near my start town, until I had it built, and I could barely get off a 2nd city by the time my teammates had 4 cities. Mainly due to the fact that his summons would kill any Villager/Worker that got close to him, and I had some good resources, and the bottom half of my cities plots which could not be gotten to without losing one of the units per turn.
Also, Computer AI doesn't really seem to know how to deal with Barbatos. I have seen a few games where Barbatos was close enough by in the beginning of the game where I could see him and keep tabs on him, and saw the computer sending endless waves of Scouts and Warriors at him, only to be killed by summons before they even got there.
I really like the feature, don't get me wrong, but something should definately be done to make sure he isn't "too close" to a Civ's starting location.