Your conclusion here seems off. We already know there were many dreadlords during the Trolloc Wars and such. We know that Ishy was free from the Seal during some of those times. Surely Ishy would've taught the male dreadlords to be AoL-level deadly? What better way to win the Last Battle than to overrun the nations centuries in advance? To control them until the Bore is ready to re-open?
There's a big, simple, reason why the Dark BT members wouldn't be as deadly as Demandred: Chosen don't like to share power.
A Forsaken is extremely unlikely to ever teach anything that would pose a serious threat to them. Nor are they likely to get too complacent around their "inferiors" - they're used to the brutal competition between channelers that follow the DO.
Part of why we had 13 Forsaken is that the others died out millenia ago; the other reason is that those Forsaken killed many of the others, and the DO killed even more from suspicion.
This trust-less working environment doesn't lend itself to "Be As Skilled As Demandred 101, mid-days in Taim's Room."
I'm not even sure that Moggy taught her pet BA anything of saidar. They had enough tools in their bag to be do what she wanted, and Moggy wasn't going to create any potential rivals. The Dark never even taught their sisters Traveling until the last two books or so.
In retrospect, it's surprising she let them keep that balefire rod...
That's not to say the BT DF won't be deadly. In fact, their training pretty much assures that they may be deadlier than the BA (they'll argue over that in an outrigger novel). Still, their big advantage may be that unlike saidar-users, any one of them can lie, make weapons, kill when they want. There are no verbal tricks that can be employed to detect their true allegiance, and boy do they have an uphill fight getting the trust of "average Randlandians."
This thread is interesting, because the "land and dragon are one" concept is something that wouldn't have anything to do with SL, unless Rand had gotten swallowed by Mashadar in ACoS, or took on Fain as his advisor, or stole that dagger and kept it with him.