For your dark side squad, stop working on Dooku and start on Tie fighter pilot. Both toons are not the best later in the game, but tie fighter pilot has a great ship when you unlock fleet battles, and has synergy with your tarkin lead. Tarkin himself has a good capital ship for fleets, and snowtrooper (imperial troopers) and talia(nightsisters) are important parts of late game squads that can be used in guild events and raids. The investment in these four will not be wasted. Farming these three imperial toons will also take you closer to unlocking R2D2, and if you focus on pheonix for light side, you will also have thrawn and emperor palpatine to add into your R2 event squad. The other dark side toon I would consider is a tank. You have Royal guard developed a bit, but to be honest, stormtrooper is more useful later in the game(at least until you get the good late game dark side tanks such as Shoretrooper and Sion).