I think its very plausable, yes Murandy is not a powerhouse nation, but it is CENTRAL to many powerhouse nations. It is near Andor, Illian, Ghealdan and Altara. The reason i like the idea of a two pronged Trolloc attack is the allusion to cohesion between North and East, South and West. Why would having a treaty with the Seanchan be so important for the Last Battle if not for a war happening down south? It would go against Jordans writing to have all of the Borderlands overrun, Lan and Mat and others slain, in order to make a war in the South plausible. Plus where did the Trolloc attack on Kylee come from? Murandy and Demandred sound like a very likely candidate.