vidian immune to blaster

Choking, Kanan struggled in vain to strike Vidian with what was left of his makeshift weapon. "Shoot him!" he said between gasps. "Shoot him!"
Hera did exactly that, leaning over the computer console and firing a point-blank shot into Vidian's back. Plasma coruscated over Vidian and fed into Kanan, shocking him. Through the pain, Kanan could see the robe that covered Vidian's chest was tattered, revealing a silver sheen beneath.
"I wouldn't do that again," Vidian said, ripping off the shreds of the garment with his free hand without loosening his hold on Kanan at all. "My skin graft is a cortosis mesh - a holdover from the days when I advised manufacturers in the field late in the Clone Wars. I can assure you, young lady - every bolt you fire against me will carry directly into your friend."

A New Dawn, ch. 43, pg. 578