I think it's just that i worry the angst might be contagious. I mean,there's so much of it that it sssccccaaaarrrreeeeesssss me. Until Tsubasa, I never would have believed anyone could have as much angst as Hakkai. (I have been proved wrong.) Then again, my terror of Fai's angst is the only thing that keeps me from being into Fai and his life partner boyfriend husband companion Kurogane. (Except that, until Clamp kills them both and makes it impossible, I'm assuming they both go back to Kurogane's homeworld and Kurogane turns Fai over to Tomoyo. She managed to rein in Kurogane's overwhelming angst and make him a mostly functional human being, she can do the same for Fai. Granted, it gave Kurogane a massive princess complex, but there's nothing wrong with that...)

I think the main difference between Zuko and Kou (in terms of development) is that Zuko's a central character, while Kou is a supporting character and (to me) has always seemed to be there to show that more conventional ideas of heroism have no place in that world. In many ways, he's a traditional hero who's been trapped in the role of the villain. If he were able to dump the honor constraints and act like Sanzo and Co. most of his problems would go away (he has to know that there's no way she'll ever free his mother, he just can't let go of the hope) but he can't take that step.