Consider that Nic now is in a much different place. His secret of how the noose can be used against him is out. Anduriel's power has been revealed, and with it, a way to counter one of Nic's biggest advantages. Nic's following has never seen him take it on the chin like that in their lives. Setbacks, yes, but not to that degree. Nic's standing among the supernatural set has taken a huge hit. He no longer has a favor he can call in from Mab. His two biggest Denarian supporters are either dead (Deirdre) or now bitterly opposed to him (Tessa). He has trespassed into the Vault of Hades and could conceivably be on Hades' list of People To Do Bad Things To.
Old Nic had his secrets intact, his followers (mortal and Denarian), his Marker with Mab, and his reputation. New Nic has none of that. He's going to be different now. How he is different, remains to be seen. He could become reckless, fearful, overly cautious, etc. It'll be interesting to see if/how Jim decides to shape Nic going forward.
I am not seeing Nic as seriously weakened. Yes he will go quiet for a bit to heal his wounds and compensate for his losses, but he is still a nasty threat
* Nic lost Dedrie, his trusted and very powerful lieutenant. That hurts in a big way
* Nic's reputation is trashed, which will make it harder for him to recruit mercenaries or temporary allies. But let's put that in perspective. All Denarians have a horid reputation as backstabbers and liars. They are freaking fallen angels. The fact that he burned some allies will make it harder/more expensive get future allies/mercenaries, but there are clearly enough bad creautres in the world that his pool of available assistance is still pretty deep.
Nic sitll has a lot of sources of power
1) obviously sitll very wealthy
2) still has the vast pool of information that Andurial collects for him
3) still has all the powers and knowledge of the captain of the Fallen
4) still has his reputation as the most deadly Fallen of them all
5) still has the Noose. And while Harry could tell everybody about that weakness, he has not to date told anybody. Even if Harry tells the world about this weakness, it is only a small weakness. Conditions have to be just right to make it work and Nic is deadly in melee combat.
6) still has at least one coin to hand out, and perhaps several more.
7) still can rally the rest of the fallen to his banner for a big operation such as occured in Small Favor.
8 ) still has the Holy Grail, an artifact of such great power that it makes the swords seem weak.
9) still Nic, one of the two most dangeorus beings Harry has ever faced. the other is, of course, Marcone who has no powers at all.