Those are all fun classes. Priest/Warrior obviously work best when paired up, but I think they're still pretty satisfying solo. Warrior has to be one of the most exciting classes hands down, but it can be frustrating if enemies keep their eye on you.
Hunter/Shaman are some of the least reliant classes and can basically do it all, so you can't go wrong there. Hunter is the supreme solo hero choice imo, mostly due to tracking but also thanks to your really well rounded kit @39.