Obviously Demandred doesn't want to give away where he is in front of Graendal. Therefore he is pretty close-lipped.

But in my view his words: "My rule is secure. I gather for war. We will be ready", would perfectly fit the idea that Demandred controls Roedran, who is building an army in the hearts of the Westlands.

As said, Bryne points out that a united Murandy could bring up a considerable number of men. Even if Murandy might be a little smaller than other countries, it doesn't mean that it's less powerful, if you read the quotes I gathered from all over the series.

Take e.g. Germany. It's certainly a smaller country if you compare it to big African countries, but I would say it has more importance. The question is not only the size of a country, but how many people live there, how advanced are they, etc. . A smaller country might be even more effective, since the ways are shorter. Plus, the location of Murandy makes it strategically very interesting.

It also fits better with RJ's comment on the Forsaken's power bases, since he said that all Forsaken want worldly power. Just controlling Taim & his 100 cronies is rather pitiful, IMO, especially considering that the BT spawned several hundred more Asha'man, who serve Rand.

Besides that, you seem to assume that it is most important to deliver channelers for the Shadow. But from all what we know it seems more important to cause chaos and usurp nations so that the Westlands aren't united at TG (especially after BS indicated that the DO has a gigantic Shadowspawn army anyway).