Demandred likely has spies among the AM and might use DF there occasionally, but he certainly doesn't control the BT. Basically just the 100 cronies are truly on Taim's side. It's quite laughable that Demandred would be proud to control these 100 channelers, if he likely commanded tens of thousands channelers in the AoL, and especially if he provided Rand with 400-500 channelers at the same time. Besides that, Demandred was a politician and General of trained troops, not a trainer or teacher himself. It's hard to imagine that someone like Demandred had the motivation or patience to train other channelers. Therefore Demandred is not even needed at the BT. Finally, the notion that the secretive Demandred ordered to paint the fist symbol on Taim's palace is simply ludicrous; he had to fear that other Forsaken or Rand/LTT might recognize it, thus it makes no sense for him to show it. It's rather likely that Taim learned about it in Ishy's lessons and considered it appropiate. Also, no Forsaken comments that the AM are built or trained like army channelers in the AoL.