And that unification specifically means towards faith in humanity and the Light.

The Dark One's army is actually very well organized, with a rather strict hierarchy of command, starting with the DO, followed by Nae'blis, followed by the remaining Forsaken, then various levels of DO ranking, including Fades and, at the bottom, Trollocs.

But the important fact is that this organized team of evil-doers is set out to split, divide, and wreak havoc. They want suspicion and hatred between everyone, they want faith in humanity lost, and they want people to give up hope. When that is lost, the DO gains his grip and the Pattern weakens. Similarly, I don't think the Seanchan help Rand's cause, because they maintain order the same way the shadow does: by force and subjugation. This is not how hope and freedom is restored.

This is why Rand is so important; because he unifies and brings hope. His opposite is Ishamael, the Betrayer of Hope.