By your account Logain would also judged Berowin as stronger than Nynaeve because she may be able to Shield him alone. That would be quiet the misconception. And in the case of two men who who are close in strength such as Rand and Logain (who it would be difficult to establish which is actually stronger from casual observation) Logain's statement is stupid. He's seen with his own eyes that a MUCH weak man, Androl, can make gateways on par with Rand so he clearly knows there is more to a gateway's size than simply the strength of the Channeler.

Where is your evidence that the Talent is rare? By all accounts in the books the Talent is actually abundant! We've seen that nearly all Channelers can Travel and we've heard that at least some, Flinn, have difficulty with it... IIRC Flinn should be able to make a larger gateway than he can. This example is probably meant to show is that Talent, or lack of it HAS an effect on Traveling and it goes both directions. There is a quote about "him not being like Androl" in there somewhere. Certainly strength is a factor, but Talent is much more likely the driver on gateway size (I think it's something of a multiplier ... Androl gets a +500% while Rand gets a +25% type of thing). Androl is clearly an outlier in his ability, but that ability illustrates the point that the Talent is what is important. It may be possible that a different weave would enable weaker Channelers to Travel.

Regardless Androl's ability proves that you cannot judge a Channelers strength by the size of a gateway.

Certainly Channelers link to achieve certain feats, but Talent with a flow would be a part of a link and we know in the AoL (BWB commentary) that strength was not the biggest factor in being chosen for a circle, rather ability was. Thus a man like Androl may have been attached to circles for mass transit, or Berowin for shielding etc ... It isn't their strength that is needed, it's their Talent.

Strength in a flow doesn't necessarily mean someone can channel more volume of that power than other flows, merely that they have a more refined touch with it or that it is "natural" to them. It's not like Egwene can channel 5x more Earth than she can Air ... Just that her Earth flows are much more pure than others. Kairen and Leane are two of the weakest AS in the Tower, yet they had more ability with making Cuendillar than anyone except Egwene. Strength was not the overcoming factor there as Nicola was likely stronger than either of these women at the time and Bode may well have been as well. Why weren't Romanda or Lelaine making it? By your rationale as stronger Channelers they should be able to compensate for their lack of Talent or flow affinity by adding power ... Romanda and Lelaine are about 3x the strength of Leane and Kairen, certainly they should be able to channel more volume of Earth into a weave ... Or why not simple secure angreal for Leane and Kairen and send them to the harbor chain? Likely because more Power wasn't what the needed.