The build-up of Oberyn, his championing of Tyrion and his head getting smashed in is one of the major reasons why ASoS was so great. You can't not have him die after all of this, even though he isn't as good as he was in the books.Not sure what you expect him to do, he's getting his face crushed but he's currently being used to introduce Dorne. The sexual aspect of him is pretty overdone though. Maybe I'm a homo but I'd rather see scenes with him clowning lannister soldiers than being a whore house.
They overdo the homo shit too much. None of it was part of the books, of course, but they still could have made their "HBO lieks teh gays" point with his first appearance this season. Every time he has a scene it opens with him wearing a LOL IM A BADASS BISEXUAL sign around his neck. It's gratuitous even for a show that is loaded with gratuity.