Dooku is plenty good and plenty “worth it” in many game modes, but the answer to whether or not you should gear him up now is always “it depends.”
What’s your focus? Raids? Arena? GAC? TB/TW?
If you are closer to a beginner, or don’t have a specific focus, I’d consider Dooku to be a luxury character to have. He’s not needed in the beginning stages for any specific purpose, and there are more important characters to level up in order to unlock top-tier characters like Revan and Malak.
Generally speaking, the consensus is that using Palp for offense instead of defense in GAC is preferable. His kit and the team you surround Palp with are very very good at shutting down specific difficult-to-deal-with teams, while also being fairly easy to beat themselves.
What’s your current GP and what teams are you currently running for GAC defense? That info could help us better answer your question