Well, beside the obvious option of Starcraft 2, I think a game that could work with those options is Imperivm: Great Battles of Rome. It's a fairly old game (15 years), and it's particular as in you don't build buildings, you can only conquer them, but it's one of my favourite RTS games, and it has a hero system where they have a few skills you can choose to get when they level up, much like WC3. Also, every unit in that game levels up (but only heroes have skills).