The problem is BS completely screws up the number of troops on both sides and the powers of the channelers.
When people ask "Why don't they do X with a gateway?" part of the issue here is BS radically expanded the uses of gateways.
BS changes it up on purpose, IMHO, because with RJ's numbers and power levels of channelers there would have been nothing for non-channelers to do. Yet, the interminable storylines of Perrin and Elayne, which were all about gathering troops were supposed to matter, as well as efforts by Rand, Egwene and Mat towards the same end.
Expanded use of the gateways comes from KoD, the attack on the manor, actually. In fact, Sanderson depowered them, making weaving them tiring, which was not at all the case in RJ's books. Jordan massively screwed up the build-up towards the Last Battle, there is no way around it. Channelers should never had been as numerous and as powerful and Travelling should have remained a rare Talent rather thannsomething that anybody can learn and anybody with enough strength/in a cirle/ with an angreal can use.
Lan's death, if it had happened at this point, would have been all the more tragic since it would have come after he embraced life. The true measure of his sacrifice was that he had many reasons to live, at this point.
I just felt that his death would have fit the theme very well. And it would have made Nynaeve's job all the more incredible. Imagine a scene where she's feverishly working on Alanna, to spare Rand the very pain she is feeling right then. And to help her deal with the pain is Moiraine, who has felt the exact same pain when her bond to Lan was snapped.
As it was, it still worked, but I felt that this was one moment when a character's death would have genuinely had a greater impact on the story than his unlooked-for survival.
1000% this! It would have made so many lacking plot-lines so much better and linked them all together.
After Gawyn and GaIad both lost to Demandred, I fully expected that Mat would be the one to take him out. A little nod to TDR.
Ugh, no. Demandred had a huge chip on his shoulder because LTT's superirity over him was "unearned" due to his ta'verenness.
It makes vastly more thematic sense that he'd be taken out by somebody who had honestly earned his stripes than by somebody who had even more ad-hoc external help from the Pattern than LTT! Against Lan, there were no excuses - Demandred lost fair and square.