Well, I’ve had DN(lone sith) in my squad lineup since unlock until I just replaced him with MT. I never zetad his unique. I have decent speed relative to my shard and I take 1st on days it’s my turn. Most other DN’s around me have his unique zeta.
It makes a difference. My DN rarely gets an annihilate off since only my CLS debuffs and combat analysis is zetad everywhere. Against me their similarily speeded DN’s get one(sometimes 2 annihilates off against me despite my efforts to stop it. We all run similar teams so it’s not poor compositions on my part.
I won without it, but it is worthwhile for lack of a better place for it.