Ten years of world war... the numbers for those Lews Therin had to convince are not so high as you think.

Some of those had to defect to the Shadow, given the circumstances I imagine a lot of people were trying to save their asses. You have to take into account attrition from battles, assasination, etc.

That the Breaking occured is evidence that the numbers of Aes Sedai were low at this point, unable to handle the males going insane left and right. Had their been no atrition, I don't think the Breaking would have occured. The female Aes Sedai were overwhelmed.

And you have to take into account a mixture of politics and ta'veren. You get a two party system set up and they vote along party lines your not going to get much done, unless one or the other have the majority. If LPD's plan was the popular (I haven't read the SaSG in a long time) one, it is highly likely that LTT had trouble finding women with either the sufficent Talent, or skills he needed.

I don't think a circle was important, because he did go it alone. It may have been a Talent.