Tarkin needs potency more than anyone else period.
He has one of the best kits in game but can't land anything. Seeing how everything about him is debuffing I feel he should have one of the highest is game.
His basic actually hits pretty well, if you need to tone that down to raise his potency so he is not op, then do it.
Tarkin has the kit to be a game changer, but his potency is why he is never used. I don't care if it does get to 130% at gear 10. He should be at that at gear 5, not 9% like he is now. No one right now is going to waste gearing him to 10. He should be hitting around 230% at gear 10.