What are you looking for? Cities, museums, architecture, natural scenery, food, beaches?

I'd probably skip Kosovo instead of Albania:

Sofia - (maybe) Skopje - Ohrid - (maybe) Tirana - Bar/Budva/Kotor - Dubrovnik - (maybe) Mostar - Split

or for something different:

Sofia - Belgrade - Sarajevo - Mostar - Dubrovnik - Split