They and the Seanchan were a major part of Rand stopping his loss of humanity and using the one power on his would be allies. They displayed kindness and showed concern and care at the end of TGS and ultimately had Rand remember his past (and the growing song!). You have to remember the last book was split into three. Not all the world touring and build up could be contained in the last battle and that was why the damn novel was too big. Sanderson should have written all three with the correct timeline and released them at the same time. Then this kind of confusion would not have been so prevalent with fans.

Other cultures:

1.) The Seanchan were hugely important (how else does Mat get to S.G. and stop Mashadar/Fain) and they were present for about 60% of the Last Battle as well.

2.) You got me there, I would have loved a combination of Borderlander and Aiel force holding the Gap with brilliant military strategy instead of the little screen time and a retreat and burn result. But the Aiel did show what kind of damage a warring society could do to the forces of light and were part of the Forsaken strategy to create multiple fronts for Rand to deal with throughout the years leading up to the last battle.

3.) Seafolk did play a huge part to a Domani (bringing the food) and that was supposed to be part of the last novel before the split. And the weather around S.G. ultimately ending in the dragon symbol was symbolic of the need for both the creator and the D.O.

4.) You should know Jordan loves to infer the final payoff instead of put it on screen. Logains glory will be earned later, We all expected it to be because of actions in the Last Battle, but I love the weakest Ashaman being the most effective OP slinger in the end, it proves that will is more important than pure strength and that was a reoccurring theme of the end.

5.) Valen Luca's traveling circus was the most pointless payoff in the series (although the final positioning of them in Ebu Dar with the cameo of Petra could mean they play a part in the Tuon/Mat outriggers) So I am going to have to hopefully one day RAFO on that one.

6.).................