Later in the series it seems they make it less abot being only one. It is more like two 'tribes'. The good Immortals who try to live without dueling and the evil Immortals who are trying to gain power. Many times Duncan walks away from fight if both parties are willing. He also takes on training of a couple of newbies so helping Dean would be very in character for him. I am in the middle of watching season four so I can't say what will happen later. I am hardly an expert. See ithidrial for that.