nihilus unique zeta?

I think it's better than his leader Zeta. If you have him on the roster, that's permanent debuffs. Zader does the same but takes a turn to get them off.

The real question is does it apply the debuff if the enemy team has tenacity up a la Rex, Yoda etc?

Yep faced a qgjz and yoda z and it still applied

Yeah, I was digging the idea of that instead of his lead and go with zMaul, ep, vader, sith troop and zNihilus unique

I just saw a video on forums, and if tenacity up is applied before Nihilus gets health down on them, it countered health down

From: https://forums.galaxy-of-heroes.starwars.ea.com/discussion/95189/darth-nihilus-4star-on-arena-maul-lead

"Any;95189" wrote:
https://www.youtube.com/watch?v=XyeWnsZ3c14

Seem we can ignore him if can not debuff well.

So better let him lead.

The health down effect can't be evaded, but it can be resisted.

"ForceMondeo;925926" wrote:

"Atlas1;925786" wrote:
I think it's better than his leader Zeta. If you have him on the roster, that's permanent debuffs. Zader does the same but takes a turn to get them off.

The real question is does it apply the debuff if the enemy team has tenacity up a la Rex, Yoda etc?

Nihilus unique penetrates tenacity up? Where does it state it as a permanent debuff

It doesn't penetrate Tenacity Up. Watch the video I just posted above your comment. It can't be dodged, but it can be resisted.