The primary goal and ultimate aim is more simple - free the Dark One. Causing chaos seemed to occur as much as a result of Rand al'Thor's victories as it did as an after-effect of the Forsaken's actions. If the Forsaken could locate all the Seals and break them immediately, then they wouldn't have even bothered taking over the nations that they did.

The problem, from a plot mechanics standpoint, is that it really works either way - it is to the Dark One's benefit if Murandy stays destabilized as well as if a Forsaken took over there. But the main concern is that Graendal's task, destabilizing Arad Doman to such an extent that it could never be united, seems completely counter to what you suggest Demandred is doing. And we need to keep in mind that Mesaana and Semirhage were tasked with using far more powerful nations and factions while they were useful but with the ultimate goal of destroying them as soon as they were done. Uniting divided lands for the sake of marshalling them for Tarmon Gaidon just doesn't seem like a victory major enough to make the Dark One laugh. It would actually be more like a regression in scope from what we saw in the series.