Except... Mesaana says Demandred wanted a sa'angreal before attacking Rand. And Cyndane is able to handle Alivia even though the latter had a powerful angreal. Both these facts show two things, I think:

1) A circle of 13 is overwhelmingly strong. At this point, skill differentials matter very little, since such a circle can shield you not matter what you try. Angreal also don't seem to help much against full circles.

2) The skill/knowledge differential between the Foresaken and modern Aes Sedai is such that they feel supremely confident of their abilities against just a few of them. It pretty clear smaller numbers can pose plenty of trouble, though (for example, LTT balks at Rand's plan to shield seven Aes Sedai, even though Rand has an angreal).

Sure, but they were clearly outmatched in terms of knowledge and skill too.

Or... Damer wasn't really pulling in the full abilities of the circle. Perhaps in the Age of Legends, such a circle would have made mincemeat of Demandred unaided. This was Damer's first time in a mixed gender circle, after all.

Except, once again, LTT thought Rand with an angreal couldn't shield seven Aes Sedai, but Rand cut through their illusion weave instead:

Not strong enough. Even with the angreal, maybe not strong enough, not to hold seven. You fool! You waited too long! Too dangerous!

With a not insignificant angreal, Rand isn't strong enough to shield seven sisters, and LTT thinks it is "too dangerous". Which makes one question the veracity of Loial's statement. Were the False Dragons unaided? Were the Aes Sedai tired and at the end of their strength? Had either of those False Dragons set up wards? We don't know the details, and in the face of that, I will trust an event in the present over histories filled with suppositions.

Remember too that Egwene thought that if she acted quickly, she could handle five Aes Sedai, but the moment they started holding the source, she said success would only last for moments. So surprise is another factor.

They weren't all Reds, only Sashelle was. Further, I don't know what skill is involved in holding a shield. What we do know is cross-gender shielding is incredibly hard, and these sisters weren't linked, but instead holding on to an already generated shield. Nynaeve is in the ball park of Logain's strength, and she found it hard to hold a shield on him too. Does this mean he vastly exceeds her strength too?

We really have very little information on strength differences needed to overpower someone of the opposite gender with shielding.

Except Cadsuane says in tGS that two women of the weakest rungs of the Aes Sedai can easily hold the shield on Semirhage. Two fairly weak Aes Sedai do in fact hold a shield on Nynaeve. So what do we take as the measure of strength: ability to shield opposite gender or ability to shield the same gender?

All told, there seems to be quite a bit of fluidity to shielding. Nynaeve sheilds Talaan, but is unable to shield Elayne. Maybe she was concentrating more at one time than the other.

For same gender shielding. And the wording has always been to the effect that breaking a shield is tricky anyway. You need overwhelmingly superior strength to have a guarantee of breaking a shield, is all we can say, I think, and gender differences bring more complexities to this.

We don't know that for cross-gender shields, as far as I remember.

As was the one on one between Cyndane and an obviously much stronger Alivia.

And Graendal versus Moghedien and Cyndane was a no contest. There are degrees of skill and issues like surprise involved quite clearly.

Was patently wrong. We have this from Elza:

Cadsuane must have had an angreal of her own, from the amount of saidar she was drawing, more than Elza and Merise combined, yet even that paled beside the Power that flowed though Callandor.
Cadsuane, we know, is barely weaker than Egwene. Merise is either as strong as, or just weaker than, Amys. Elza is definitely weaker than Melaine. Yet, for Cadsuane to be drawing more than Merise and Elza, she had to have an angreal, according to Elza. Isn't that much stronger proof than Aviendha's vague, and uneducated statement?

A mostly refutable list, I think.

Now, I'm not saying that Moiraine is definitely 80% of Lanfear's strength. But if it turns out that way, I'd have no trouble accepting it. I never did put as much stock at some of those character statements like you did.

He probably does so by pointing out characters are wrong all the time, and what matters is actual events and observations, not suppositions and statements.