Zeta Reworked Tarkin Review Video

I'm not exaggerating here in the least -- Most recent Rancor Raid, I have Zeta'd Tarkin's special, counted up to 60 consecutive basic attacks -- six-zero -- and I don't see any difference in damage than what he was doing pre-Zeta. I feel filthy, what am I doing wrong here? (fwiw, Gear XI, over 85% Potency)

I'm going to continue test-driving here (what other choice do I have?) but so far, I feel like this was the worst decision I ever made with this game. Awful. Save your Zetas people.