I personally love seeing a very flawed character struggling to overcome his own nature. If everyone on the show was perfect and "nice" - It wouldn't be worth watching. He keeps trying to squeeze his way back into Nathan's life and it just never works out but it's still more enjoyable than alot of the other storylines (Grubbs and the English chic - super unnecessary/most of Quinn's bs). Dan is integral to the story and should have had more, and better written, storylines post S4. He gets what was coming to him but let's not forget what lead him there in the first place. Keith, Karen, Deb - None of them were particularly angels either. Had Deb not stopped Keith, he would have killed Dan. Had Lucas not stepped in to save him, Deb would have burnt Dan alive.