Alivia was likely as much as 3x as strong as Cyndane during this battle thanks to that angreal...

TPoD
Unweaving

Elayne's POV

Stripping away the decayed cloth revealed a small amber brooch in the shape of a turtle. It looked like amber, anyway, and it might been amber once, but when she opened herself to the Source through it, saidar rushed into her, a torrent compared to what she could draw safely on her own. Not a strong angreal, but far better than nothing. With it, she could handle twice as much of the Power as Nynaeve, and Nynaeve herself would do better still.

So if Elayne is handling 2x as much of the power as an unaided Nynaeve that means the turtle is giving her an increase of at minimum 2.5x (over her natural strength).


TPoD
A Quiet Place

Elayne's POV

One was an odd piece of jewelry, a golden bracelet attached by four flat chains to finger rings, every bit of it engraved in an intricate mazelike pattern. That was the stronger of the two, stronger than the turtle still in her pouch.

You'll note that Alivia is wearing this angreal when facing Cydane. We know Alivia is stronger than Nynaeve and that this angreal must offer more than a 2.5x increase in strength. Never mind the ter'angreal she also wore! Also Elayne more than implies that Nynaeve, as the stronger, would be able to get more amplification from the angreal... logically Alivia would do better than Nynaeve.

Here is what RJ had to say in his Blog, ironically to the very poster who dismisses skill!

- For Sidious, when Alivia faced Cyndane, Alivia was by far the stronger because of her angreal, and had various tools (ter’angreal) to work with besides, but Cyndane was much, much more knowledgeable about channeling. Alivia, after all, knew relatively little except how to be a weapon. That was very useful in the situation, but in this case, knowledge versus strength made it an even match.

And you'll note that Alivia in fact came off the loser here ...

WH
With the CK

Alivia could not stop staring in wonder and flexing the arm that had been broken as well as seared to the bone.

So I think it's safe to say that a more skilled channeler can face a less skilled one who is 2-3x as strong as them (depending on the difference in skill and the situation of course). In effect Daigian could theoretically take out Moiraine if she was dramatically more skilled (this is a hypothetical based on their strength not an opinion of their skills!)

So why didn't the other FS do better at the Cleansing? IMO ... because they didn't really want to be there. We hear as much from Demandred, Moghedien and Osan'gar.

WH
With the CK

Demandred: Any use of the Power would warn al'Thor. He would have to wait until they passed.

His original plan was to not engage them at all and he clearly knows he only has moments before he's attacked by the circle holding Callandor.

or Demandred had this to say

WH
Wonderful News

Bending his neck hurt Demandred as much as speaking those words. So they would take al'Thor — while he was trying to use the Choedan Kal, no less, he and some woman drinking enough of the One Power to melt continents!

WH
With the CK

Moghedien: Only the threat of Moridin's hands caressing her cour'souvra had driven her to Travel here at all, and she had delayed coming, prayed that it would be over before she was forced to.

WH
With the CK

Osan'gar: Crouching again, he bit his lip. This forest was a very dangerous place, more so than he had expected, and nowhere for a genius. But the fact remained that Moridin terrified him.

Obviously Moridin's earlier orders as NB forced them to appear, but at best they were half-hearted about it and for the most part wanted to get the hell out of dodge rather than risk the battle. Seems to me that the FS were at best trying to avoid getting killed rather than really focusing on killing their opponents... with the possible exception of Cyndane who rabidly wants to see Rand dead.