Moghedien says Nynaeve stands no chance against Rahvin's overwhelming strength. She says this outright.

Graendal says she will never dare face someone directly if he was able to overwhelm Rahvin and Ishamael. Not just Ishamael, but Rahvin too. And Rahvin is not even as strong as Ishamael.

These two quotes indicate that there is a significant gap between the average female Forsaken and the male Forsaken.

And yet Lanfear is supposedly able to stand against the top male Forsaken.

This indicates that there is a significant gap between Lanfear and the other female Forsaken.

This is reinforced by the fact that Cyndane is weaker than Lanfear, but still stronger than Graendal.

Now, whether Nynaeve is at 75% or 85% of Lanfear's strength cannot be said for sure, but since Graendal is likely one of the 6 women stronger than Nynaeve, and Graendal is weaker than Cyndane, who is weaker than Lanfear, that makes it clear that there is a significant gap between Nynaeve and Lanfear.

As for Egwene and Elayne: They were both further advanced in their development in tSR than Rand was in his development, and yet he manhandled them both together with ridiculous ease.

I am happy to concede that both of them would still have grown in strength after that, and significantly so, but so would he.

In fact, both of them could already control the Power far better than he could, comparatively speaking, at that point in time.

I have no doubt that the strength comparison between Rand and the two girls remained in pretty much the same proportion for the rest of the series, as all three of them grew in Power.

In fact, Rand may well have overtaken them even further as he leaped ahead in strength the way men do when they channel a lot.

Bottomline: Rand is double Egwene's strength at least. And that means Lanfear is close to double her strength as well.

Of course, you deny direct quotes such as the one from Egwene herself where she says she would be helpless against even Moghedien, whereas Nynaeve would be able to match Moghedien.

This despite Egwene being more skilled than Nynaeve. This is the clearest possible indication that Nynaeve is significantly stronger than Egwene. And this while Nynaeve is only at Moghedien's strength, not even her full strength yet, which will significantly exceed Moghedien eventually.