The Shaido was by far the biggest clan, and I think it had as many Wise ones as at least 4-6 of the other clans. I can't reference this as I don't have the books with me, but that was the impression I got.

At the very least, the Shaido made up 1/3 of Aiel warriors (and all Aiel are warriors) in TFoH/LoC, so I'd not be surprised if there were far fewer channelers than you assume. I'm guessing maybe 1,000 at tops (remember, many can't channel - Perrin's group worked under the assumption that all 500 could, when it was more like half that number).

Also, remember that like the AS, the WO have their own goals and motives. They care nothing for Randland, only that the "remnant of a remnant" is saved, and that it is as large as possible. Even Avihenda puts this goal above almost everything else.

Similarly, the Sea Folk are tied to the seas. Only the Kin, AS and AM are tied to Randland, and have a vested interest in keeping it intact and safe beyond winning TG. The AM are divided between Rand and Taim, and the Kin have not yet shown leadership or political ties, nor weaves of warfare (though as you say, gateways can count for a lot in that regard).

So yes, I agree that especially since TDR (or around then), we've slowly had our esteem of the WT chipped away at (and with good cause). But there is still massive potential for good there, and uniting the tower was the first step in reaching that potential. Egwene has a LONG way to go if the AS are to become truly useful to Randland, but without Egwene as Amyrlin they were heading towards Mesaana's vision of a tower which unknowingly served the DO. Elaida certainly caused Rand substantial troubles (distrust of female channelers [even Cadsuane and Nynaeve], issues [as of yet, not entirely explained] in the BT, not to mention nearly delivering him into the hands of Mesaana herself).

Egwene can still botch things up, but if she plays her cards right, the Tower could play a crucial role in TG. Think of Min's vision of specks of light being swallowed by blackness - Rand will need EVERYONE he can get.