Callous Conviction Zeta: Opinions

I put a zeta on Callous Conviction and don't regret it. I run the same arena team as OP. Finish top 50 in arena everyday and 1st in fleet. The speed makes a big difference for me on the executrix. In arena its not a game changer, but I've got him at 110% potency and when you've got 5 debuffed enemies he doesn't take damage, especially if you've stacked with his basic. It also makes his aoe hit pretty hard. I've hit for over 20k on his aoe in arena. It can make or break a close match and is useful in both arenas so why not?