I think it is more than his character is compelling, whether or not you agree or disagree with his actions or the reasons for those actions. I don't think the developers or writers are trying to push anyone's noses into the water to get them to drink it, as it were; they are only dwelling on characters whose actions and rationales are important to the story being told. You don't have to agree or disagree to concede that Saurfang is and will be important to the story, just like Sylvanas, Baine, Anduin, and Jaina are.