Single hard node characters are simply a fact of the game. Sabine is not the worst you'll face. She's nothing compared to Shoretrooper, Nihilus, Baze, Holdo.
But stick to it, and in time, you'll have her at seven stars.
Though I do agree, the guild shop needs to be redone, and removing Sabine from it was a mistake.
DarthDuck: Sabine is not the weak link. Her damage output is on par with Ezra. Her ability to spread expose and stagger with her detonator is equally good at setting Zeb up for stun, if not better. She's competing with Kanan for best Zeta on Phoenix. Her darksaber and detonator are Phoenix's two best tools for breaking hard targets like KRUM and Savage, an attribute Phoenix desperately needs, and the darksaber is a fantastic force multiplier against raid bosses.