So let’s say you’re right & Lash couldn’t paralyze Harry but could only incapacitate him for a few moments and/or make him significantly less effective in the short-term. Wouldn’t this be just the opening Maeve needs to take out Mab? Maeve & her retainers (or she could call in the Walkers to help) are powerful enough that a temporarily weakened Mab is all they need to remove her (like a few minutes). Killing Mab would put Nfected Maeve on the throne, giving Nemesis exactly what it wants regardless of the other advantages you’ve listed.
It depends on how weakened she was. Mab is stronger than Maeve by an order of magnitude--if Maeve is power level 10 then Mab is power level 100. Even if Nemesis can cut Mab's strength in half, she's still way stronger than Maeve. And even if Maeve's allies can make up the difference, Mab can call on all of Winter given half a chance, and unless Nemesis can suppress something on the order of 90% of Mab's power, she's going to get that chance.
Mind you, this might be plan B, or plan C, D, or E, but it makes much more sense for plan A to be: let's throw someone we already want dead at Mab.
Also remember how the Nfection deals with Cat Sith - it takes him out in seconds. Remember Rasmussen from DM who had been enslaved by his Fallen. Just because it didn’t work on Harry doesn’t mean Harry/Lash is an accurate model here - in fact JB goes out of his way to show how unusual the Harry/Lash situation is. As an immortal without much in the way of free-will, I’m not sure how well Mab would be able to oppose Nemesis.
Clearly Nemesis can be opposed by non-free willed beings, because Lea did so. And Mab seems to be strong-willed enough to be the Sidhe equivalent of Harry in that department. We don't know how from people he doesn't like (as opposed to maliciously subverting them on general principle). He may do things like bring Harry a warm coke, but he doesn't do things like delivering the coke via dumping it on Harry's head. This doesn't mean he isn't strong-willed--Harry will (usually) obey orders from the White Council, even if he doesn't like them much--but it's not a point in favor of him being particularly Nemesis-resistant, either. Mab, on the other hand,
is Mab. That is to say, even when compromise would be useful to her, she doesn't use it. She does things like challenge Harry to fight her on Demonreach and slam his head into an elevator wall, even though Harry would be much more cooperative if she refrained from doing so and explained things, even if that explanation was just "I know I can't force you to act against your principles, and I'm not trying," rather than anything concrete. This, I feel, demonstrates the kind of stubbornness that would seem necessary to fighting off something like Nemesis.
Also note that I'm not claiming that Mab has had to fight off Nemesis for years alone--only long enough for someone like Mother Winter to give her some help with that.
Perhaps she is less effective from books 4-14 because she is operating without a Winter Knight (meaning her main tool for meddling in the mortal world is nonexistent) & without her top 2 lieutenants - Lea & Maeve. It also didn’t help that Nemesis’ latest salvo came from an angle she didn’t see - Aurora. That caused a massive chain reaction on the Summer side as well, leaving the Courts out of balance (Lily should never have become Lady).
However by the end of those 10 years, she got a Starborn as Winter Knight, healed Lea & replaced her old, neglecting her duties for 150 years Lady with one who is very capable instead. On the Summer side, Titania has calmed down somewhat, Fix has been trained to become an effective Knight & Sarissa (who has the right training) becomes Lady.
All the beings/ powers that screwed with her or her Accords have gotten a major reckoning - the Reds were obliterated in a battle that was fought by her Knight, Lady & #2 (even though Molly didn’t do much, the outside world will not see it as such). The Denarians who screwed with her have been left ruined or destroyed. It does not matter how much of this was explicitly planned by Mab - it happened because of how she had well she had prepared her resources/ allies/ forces (explained in her chess metaphor to Harry at the end of CD).
I just feel like Mab has been using too much gambit roulette and not enough batman gambits, which would seem more her style. There could be many reasons for this, and one of them is Nemesis.
In particular, her handling of Harry is...odd. She probably couldn't ever get Harry to like her, but the way she handles him seems to actively encourage him to want her dead. So...either Mab is slipping, possibly from Nfection; or she wants Harry to kill her, probably because she's Nfected; or she's massively misreading Harry, probably by expecting him to be rational enough not to kill her no matter how much he wants to, which is a possibility.
I don’t think that the Sight is restricted to those with White Council ability - I mean I’m not sure if Beckitt or Anna Ashe were able to use it, but I’m sure people at Snakeboy’s level are.
The RPG says that it's a wizard-power, not a sorcerer one. It's unclear whether Denarian sorcerers would have it--on the one hand, the Fallen offer far more training than sorcerers usually get, but on the other, I feel like the Fallen could do something similar for their hosts rather than teaching them, and they have reason to want their hosts to remain dependent on them.
I think that none of the Denarians have the Sight, because if they did then they would have used it to see through Ivy's veil at the Shedd, and they manifestly didn't do so.
