I don't know if you did your Croatia trip already, but I did a similar trip in November (Zadar -> Pula (+Rovinj, Piran) -> (via Zagreb) Dubrovnik -> (bus) Split -> (bus) Zadar) and it was wonderful. I wouldn't skip Istria. Pula's amphitheater was very neat and almost completely deserted, and Rovinj was breathtaking on a sunny day and not crowded at all. Dubrovnik is way more expensive than the rest of Croatia, and still packed with tourists in the offseason, but it's impressive enough that it's still a great experience to walk the walls and old town