Most likely there were more powerful women in the AB years, but that doesn't mean there was a big swing in the percentage strong women represented as the Tower had many more Aes Sedia then too. Sure there would be a few women in the top 10 levels (maybe even 100+), but it had been nearly 1000 years since the AoL when the first False Dragon came on to the scene (at least the first one of note). Suddenly coming across a man at such high levels would be unexpected since the Reds had already had hundreds of years to thin out the gene pool. By the time of Amalasan and Stonebow the Tower had certainly declined.

I don't think there was any question that Logain could have broken free of her shield, but let's face it that's not one of Nynaeve's strong points

Rand Stilled 3 women at Dumai's Wells but aside from that we learned something of note in the way Aes Sedai operate with a Powerful male Channelers. They don't actually link to shield them. It's very clear from Rand's exploration of the shield that each woman was holding a separate part of the whole, coming together in the "soft spots" that later were knotted and Rand figured out how to break free of. When women link it all becomes one flow from one individual leading (like the Bowl of the Winds circle). This clearly was not the case with the women shielding Rand at Dumai's Wells and likely was how Aes Sedai tradition worked for False Dragons. Possibly they moved to this system because so many False Dragons over the centuries had armies that would need to be fought off and an Aes Sedai in a link can't function as an independent Channeler and they knew they may have needed to serve multiple functions.

I also think it's clear from the text, as well as from an RJ quote (IIRC), that men are more difficult for women to shield than other women are, so a level 1 woman would theoretically struggle to shield a level 1 man whereas we know a somewhat weaker woman can maintain a shield on a stronger woman (i.e. a Level 8 woman can maintain a shield on a Level 1 woman)