It's a bit hard to theorize about this, because the way the book has been split, but here's my take:

Aviendha has left for Cold Rocks hold over 2 (WOT) weeks before Rand went to Dragonmount. Normally, she entered Rhuidean before Rand's epiphany, close to his darkest hour, and Rand was one with the Pattern.

At the time, Rand was becoming estranged from the Aiel, falling into darkness, and was still completely obsessed with enforcing peace with Seanchan, ie: he wanted a truce for the duration of TG (in effect, had he succeeded, Rand might have preserved this way a fair deal of the strength of the Seanchan in the South, while the North post TG would have been much weaker). Several groups, like the WT, the Aiel, Andor, the SF, fully intend to wage war on the Seanchan later.

I think Aviendha has seen the future has it stood at the peek of Rand's darkness. If he destroyed the world, the Pattern would have ceased, and this future cannot be foreseen by the Wheel. The same thing if Rand went to the Shadow, or lost the LB (this is in part why no prophecy can predict if Rand will win at TG, and why post-TG prophecies are not as reliable and will come true only if the Do is defeated. The chaos in the Pattern makes newly made prophecies less certain to come true as well) So, the future the Wheel is preparing now, and that Aviendha got a glimpse of, is "unreliable". All the Wheel can prepare for is this: if Rand doesn't destroy the World, if Shai'tan doesn't win, then here's the future the Pattern as things stand right now will lead to.

I think Robert Jordan most likely intended this dark vision of a dark future to be revealed at the peek of Rand's darkness. It was meant to pile up with everything else (Perrin in a deadlock, Mat planning many things but being blocked from moving ahead by not meeting Elayne, by Verin's letter etc. Egwene having basically lost all power to influence events, Rand and Tuon clashing and Tuon deciding to attack TV and doing it and stealing Travelling - putting a dark price on Egwene's victory, Rand getting madder and madder, going dark, dark, dark, beginning Balefire rampages etc.) Aviendha's vision was to come right in the middle of all this, perhaps around the time Rand nearly killed Tam and nearly balefired the Seanchan, and make us go "jeezz... it's really going badly, how the heck will things be turned around... and now, this bleak ending too? Ouch!" Aviendha saw a future where real Light was little else than a memory... The bottom of the barrel was reached, and Rand went and got his epiphany...

The way Brandon showed Rand's epiphany early, he has diluted the piling up of darkness Jordan was planning until that moment (IMO, he also moved the demise of Mesaana to a post-reunification time (which was really useless in the context of a single-volume AMOL, but not in the context he needed a threat of some kind for Egwene to deal with in TOM, and a way make it so that this fight could happen in TOM because Perrin was involved). Based on the timelines, my hunch is that Jordan originally planned to have Mesaana launch that attack in TAR right when Egwene won the Tower, at a "TAR meeting" she called to announce to all her allies she was now Amyrlin (it would have been dramatic: she got rid of the BA, and bang... almost right away they attack her in TAR with Mesaana, while her body was nearly killed by Bloodknives... and all that when we still confused and wondering if Gawyn had already saved Egwene as in her dream, or not...). I think Perrin made only one visit to Tar Valon. He saw Rand on DM, and fought with Egwene against Mesaana - all at the same time. The aftermath of the Epiphany would have gone this way: Perrin forges his hammer, Egwene has really cleansed the Tower and is about to meet Rand, Mat gets out of Ghenjei with Moiraine.

So with Rand's epiphany, I think the dark future seen by Aviendha is already in part averted. At the peek of his darkness, Rand had closed the possibility that the Aiel return to their peaceful roots. The post-TG world would have had no place for them. Rand's epiphany has re-opened the door, and now it's up to the Aiel to make their choice. Aviendha is now aware that her tie to Andor/Elayne is important, that the project to remain warrior and wage war on the Seanchan is a path to destruction, and Egwene has opened the door to closer ties between Aiel and Aes Sedai, the Seanchan are already valueing and protecting the "Leafers". It's now up to Aviendha to convince the Aiel of the path they must take.

If anything, this makes the identity of Nakomi even more mysterious. That she was associated with the Shadow just doesn't fit. She was way too knowledgeable in Aiel ways to be Verin. I get the feeling we will have no more answer to who - or what - she was than we ever learned for sure if the Creator spoke to Rand in EOTW. My feeling is that she was an Aiel woman who the Creator "borrowed" briefly to speak to Aviendha, remaking reality to make her appear then and there. This woman make have woken up after, with a memory of a strange dream.