Slider to control Barbarian AI aggressiveness
I'm suggesting a Game Setting to adjust Barbarian AI aggressiveness. At it's lowest setting, Barbarians will just roam around and not attack players until they either attack first or are within a certain radius. At its most aggressive setting the Barbarians will constantly seek out and attack the player (pretty much what they do now).
The radius idea might be the best way to implement this. What the user would be setting is the radius of a sphere around the AI that only attacks things within it.