Her Sig is Officially on FRAUD WATCH (half joking)
If you've kept up with her kit, Nicole's signature weapon has an insane base ATK on top of a pretty impressive passive.
However, I've seen a lot more talk about the base ATK rather than the passive. I think it's important that we understand that if you're planning on building Nicole very well, this priority should be flipped for you.
Nicole's larger ATK buff is based on her own ATK, which makes a weapon with high Base ATK very appealing. This has been kinda beat into us from the calcs showing us how hard maxxing this buff at 4K ATK really is.
All these calcs, you should know, are made at a baseline that many of us are going to exceed. Nicole ONLY cares about ATK and sometimes ER%. So a lot of us are going to reach significantly higher ATK on non-sig weapons (Atlas, Oath, but particularly TTDS).
The fact that the ATK buff from TTDS is often calcing HIGHER than what can be gotten from maxxing her ATK is telling because you can always get better artifacts on TTDS— while on her Sig you will eventually hit that hard cap.
So while the passive on her Sig is awesome, keep that in mind. If you're planning to really min-max her OR you're planning on farming the other set aswell, the value from her sig will lean away from the high Base ATK and toward the DMG% passive.
[ALSO. If you are planning to farm really good peices from the new sets, remember to save your fragile Resin for Stygian Onslaught: Disturbance Outbreak, where you get more artifacts for your resin]