It makes more sense that Moridin/SH are closely controlling Taim. Demandred didn't know Rand's AM and was even surprised that Flinn could be one of them. That strongly suggests that Demandred isn't that closely involved with the BT, except for having a few spies there. It's also wrong that Taim's faction is that powerful. Actually it would be pretty pitiful if Demandred just managed to get those 100 DF Asha'man under his control, compared to the many hundreds of channelers who will fight for Rand. Demandred's words in TGS actually indicate that he has a nation under his thumb and is gathering an army. This most likely points to Murandy.