I think in Tel'Aran'Rhiod, power and having multiple opponents/supporters doesn't matter as much as your willpower and ability to intuitively create scenarios that your opponent can't counter. Considering that certain desires and actions in Tel'Aran'Rhiod manifest themselves in the real world, it is possible for Egwene to Dream herself near a Forsaken, locate them by something they are doing, Still or Gentle them within Tel'Aran'Rhiod, and then wake up, without the Forsaken even knowing who did it.

Also, I think the problem that the Forsaken has is that the gulf separating the Third Age channelers from an Age of Legends channeler is knowledge and skill not strength. Thus a weaker channeler during the Age of Legends was quite a considerable threat due to their skill. This, IMHO, is exactly why Moghedien's comment to Nynaeve when she first met and Compelled her was merely "You might grow to be something some day" (ie: her potential, while standing above Moghedien's, was not enough to automatically classify her as a threat). Thus a truly creative channeler like Moiraine, Egwene and Rand have always given the Forsaken challenges that were not quite in line with the expected outcome because their potential as individual channelers stands above the Forsaken's potential.