If there is a clear threat to the Dark One, in that he is vulnerable for a short time to being resealed into his priso, call it a "window of opportunity" time for Rand, then if I was the Dark One, I would approach this very differently.

Withdraw all my forces from the Blightborder, and concentrate them around Shayol Ghul. Use my Power to set up a massive defense around Shayol Ghul until such time as the window of opportunity for the Dragon has passed, and then destroy the world at my leisure.

If the Dragon should then break the Seals, I as the Dark One would have my FULL POWER ready to repel his desperate attack. Once it is foiled, I can extend my grasp over the rest of the world.

Manage your risk, don't gamble, as eternity appears to be at stake here. Don't play games like Moridin has been doing. Approach this much more systematically and methodically.

Secure the area around Shayol Ghul absolutely. Then wait for your Prison to weaken of its own accord. If the world cannot even hold back the Trolloc Hordes from fortified keeps and defensive positions, then there is no chance in hell that they will be able to defeat the entire Shadow horde on the Shadow's OWN territory at Tha'kandar.

Instead of stretching his forces and incurring massive losses like the attack on the Manor, Maradon and other useless conflicts, mass the defenses around the Pit of Doom and bide your time.

That's how I'd run this war if I was the Dark One. This would remove the one hope that the Light might have of snatching a surprise victory, and would then leave all eternity for the Dark One to take over the universe.