seriously, no one is arguing that the increase gets greater with a larger circle, but the fact is we pretty much don't see ANY increase with the smaller circles. If a circle of 13 can give a effective increase of 100x even a circle of 3 should give an increase of 2x ... we've even seen some instances of a pretty intense increase for mixed circle ... even a circle of two in this instance seems to have a pretty significant increase over what Nynaeve expected.

KOD
Chapter Twenty
The Golden Crane

Suddenly fires bloomed below, six enveloping dead Trollocs in front of Malevin and Aisling, seven in front of Sandomere and Ayako, and she squinted against the blinding glare. It was like trying to look at thirteen noonday suns blazing in a cloudless sky. They were linked. She could tell from the way the flows of saidar moved, stiffly, as though they were being forced into place rather than guided. Or rather, the men were trying to force them. That never worked with the female half of the Power. It was pure Fire, and the blazes were ferocious, fiercer than she would have expected from Fire alone. But of course they would be using saidin as well, and who could say what they were adding from that murderous chaos?

Why wouldn't Damer's Circle in the Cleansing have had such an effect? In pure strength measures Flinn, Corele and Sarene would be pretty strong, at least as strong as one of the female Forsaken. Neither Sarene, nor Corele are weak AS and Flinn is one of the stronger Asha'man ... couple that with "precision bonus" and noting it's a mixed circle, which is clearly even more potent and they should be more than a match for Demandred, yet they barely equal him. Again, read Demandred's quote, it's clear this mixed circle has at best a small advantage against him as he is caught by surprise yet still managed to fend them off and escape.

During Rand's captivity 6 women could "barley" hold him, and if fewer than 6 had held Logain he could have broken the Shield ... the point here is that there are inconsistencies in the effect of a Circle. Despite the author's quote, the most potent effects we've seen are when a circle is used in conjunction with a Talent.