Imperial Troopers are definitely worth it.
However, I would recommend this course of action: Get your phoenix to 7* so that you can 7* Thrawn. Get your Veers and Thrawn to 7* that way you can 7* R2-D2. After you have 7* R2, you can get CLS. CLS will change your game significantly and allow you to basically do anything.
After CLS I'd say farm ImpTroop/Nightsisters as a side project but mainly farm for JTR, who will change your game as well. However, you seem to prefer dark side with Empire and Sith, so I'd also farm up your Sion, he deserves a lot more love than you're giving him.