Where is Wulfharth in Skyrim they should have at least some mentioning of him he's kind of a big deal. Think maybe they'll add something for him in dlc?
His plague is in Windhelm, and he's mentioned by Jarl Balgruuf. The books from previous games mentioning him are all still present as well. All told, he's mentioned more times than in any previous game.
And did it ever occur to you that the devs might be holding out for DLC to use Wulfharth as a concept? Not all of the content we're going to get has been released yet.