What does Aes Sedai mean here, though? They are not of the same strength at all. If you're saying Cadsuane=1.5 Moiraine, and so on, I disagree.

When women of such strength are in the vicinity of PoV characters, they get mentioned.

First, there's Egwene's quote, then there's Romanda's wondering where Bode will end up. Not something AS do often.
And the Two Rivers hoard of pure gold has been mentioned several times.

You're ignoring the fact that the Wise Ones around Aviendha have probably come across most of the other WO, and therefore, when they comment on Avi, they're commenting on the Aiel as a whole. It doesn't matter that we don't know the names of each and everyone. Avi's strength is so rare that the WO comment on it.

So? He says Moiraine at her current full power and skill level is puny.
He dismisses the current abilities of the three, and rightly. But we're arguing about their potentials, no?

Be'lal says "they". Not one of them, they!
Moggy too makes a clear distinction between Elayne and Nynaeve, and makes it clear Elayne herself, even in her current level, is strong enough to be trouble.

That when we compare women with "Aes Sedai" we cannot use Aes Sedai to mean a woman of Merise or Moiraine strength women.

And all these six women were of Moiraine strength? I think not.
Look at the circle holding Logain. None were at this level, and its highly unlikely that women of Sheriam's strength were holding it either.
From what Cadsuane says in tGS, usually the weakest women are given the job of holding shields.
Here's the quote:
There were several others in the hallway with her—Daigian, Erian, Elza—whose turn it was to maintain Semirhage's shield. Aside from Cadsuane, each Aes Sedai in the camp took turns. It was too dangerous to risk forcing the duty only on the Aes Sedai of lesser stature, lest they grow weary. The shield had to remain strong. Light only knew what would happen if Semirhage got free.

Assuming that six women of Moiraine's strength cannot tackle Rand is insane.

I think you're mixing up shielding with battling. I doubt LTT would say no three women could defeat him in battle unless one was Semirhage, simply because Sermirhage herself is quite capable of taking him.

That was Elayne, who has no great experience with angreal. Verin and Graendal are a whole other thing.

But Alivia is not skilled at all compared to women like Cadsuane and Egwene. This is proved by Alivia's continuous attempts to make Cadsuane teach her.

Which is why I dismiss her statement that she cannot tackle one of the Forsaken linked with Lelaine and Romanda.

Yes, exactly!

Yup. Maybe Asmodean as well.

One sister of Katerine or Silviana's strength. Two such might well be able to hold Nynaeve. This says nothing of their relative strengths.
There's also the issue that Amys is unable to shield Egwene when Egwene wasn't even at full potential.

No, she is shown to shield them when they lose concentration. The same was not the case with Elayne, and hence her shield failed.
Same with Verin and co. against Graendal. They were not overwhelmingly stronger than her. Thus they couldn't shield her because she wasn't distracted.