I finished my Dark Mode game a couple days ago. Went with a Sign heavy build except for a few skills in the Swordsmanship tree like increased roll distance and less damage from backstabs. My main potions were Swallow, Petri's Filter and Tawny Oil with the liberal use of Grapshot and Dancing Star bombs when I had depleted my Vigor.
Last May, I chose Roche then I played again and chose Iorveth. For my third, Enhanced Edition playthrough, I chose Roche again. What I love about The Witcher 2 is there is no wrong/right/Paragon/Renegade choices. Each side has their heroes and their assholes.