Visas Marr - the Anti Sith?

Update her unique a little bit: "While Visas Marr has no debuffs, she has +100% counter chance, +80% tenacity and a 60% chance to Assist when another ally attacks Sith enemies once per turn."

Plenty of unresistible debuffs out there so she's not impossible to debuff, but that way she would be good for a while, and then when she's debuffed you can cleanse her and she'll be back to having a good time.