Actually, Logain's group did use Deathgates etc. They were not called such because we see them from Elayne's POV and for once Brandon remembered not to have a character who shouldn't know a name use it (like he got everyone magically adopt Moiraine's metaphor of "bubbles of evil", for instance.).
Elayne just spoke of the Asha'man using gateways that moved toward the Shadowspawn. Briefly... as after making us go through pages and pages of non-channeling warfare described in way too many details (Brandon seemed to go through notes from his "military advisors", not nearly enough comfortable with these aspects to turn the whole thing into good drama) he had the big channeling battle following the Asha'man's arrival at Cairhien to finish off the Shadowspawn happen mostly... off-screen after he got his big "wow" moment with Androl.
But yeah, on military matters this was Brandon's biggest weakness. He deprived the Light of its biggest single group of channelers (the WO who could channel, estimated anywhere between 1500 by the cobnservatives to 4000+ by the generous), and those would have changed everything. Aviendha likely could easily have had 1000+ channelers with her at Shayol Ghul (instead she had a handful of WO to whom she had to add sworn AS or Cadsuane followers to be able to from two small-ish circles, and Sorilea spoke of asking for off duty Windfinders to be able to complete a third circle!), forcing the Shadow to use completely different tactics. The Shadow should not have even tried to force its way into Thankan'dar, the Light's channelers would have butchered the Shadowspawn in the narrow pass to the point it made little sense for them to even try. That was a battle calling for sneaking Dreadlords using the True Power, for Graendal compelling random people to commit assassinations, for "kamikaze" Grey Men infiltrations, dropped by the Dreadlords among the channelers at night to attempt to assassinate as many of them before being killed, for waves of Draghkars not letting the channelers rest, for the huge packs of the Dark Hunt unleashed in the night that the Light could only kill by the balefire they couldn't use, for Myrddraal sneaking in every shadow in their camps to kill women from dusk to dawn.
Even given the Thankan'dar front a 1000 women instead of all the WO, that would have left Lan with a few hundreds WO, also changing completely how Brandon needed to approach that battle, forcing him to make Taim's long foreshadowed "superior training" come into play.
That still allowed Elayne a few hundreds WO with Bael as well, more than enough to keep channelers out of the field and in reserve for retreats by Gateways and circles for healing etc. More than enough channelers for not having to cheat and get rid of what RJ had set up: Elayne as overall commander yet unable to regain reliable control of her channeling until she gave birth.
Instead Elayne had paltry numbers, Brandon forgetting to even mentions the small group of WO she had (with Edarra, joined by a few extras) in most of her scenes (they're there once, then Elayne forgets them, then they're mentioned again etc.). And even splitting things that way, that left enough WO to at least double the numbers of women on the Kandor battlefront. No wonder RJ had to give Demandred a whole continent's worth of Ayyad and a powerful san'angreal to turn the tide.
Brandon also misrepresented the Windfinders. They had four battlefronts and Mayene to supply, for the light's sake. That's a job for maybe a hundred women working in shift. Then the Windfinders couldn't use more than a circle of 13 to operate the Bowl of the Winds, again a task for maybe 50 women working in shifts. Sure, they could have increased that if a few Asha'man got assigned to them so they could enlarge their circles, but that's pointless since we know that exceeded the capabilities of the ter'angreal. Add a task force of Windfinders to protect the others (because they should have been a primary and constant target of the Dreadlords through the whole battle...Brandon had the Shadow leave them largely unhindered, when they were what stopped Shai'tan from unleashing the mother of Storms on the Valley and beyond..)
Anyway... Traveling between the fronts shouldn't have been so complicated.. the Light had enough Windfinders to provide each fronts with a decent sized group which duties would have been only that.
That got rid in turn of some of the geographic impossibilities Brandon artificially introduced... masons having to build bridges over the Erinin. The Erinin! There's no way the Band's masons could technically do that short of having help from channelers with bridges of Air, let alone do it so fast. Both the Erinin and Alguenya are very large rivers, and while there are shallows and mudflats in that area, big trading ships can still navigate it. That's too deep, too wide for mere military masons to bridge with rudimentary means. Rafts or Gateways it needed to be, forcing the Myrddraal to build rafts of their own to follow... at least big enough an army attempting it to keep the Light focused there... then... ooops... they're were two Portal Stones nearby for the Shadow to send new armies very very close to Cairhien, and two Waygates... if the Shadow could re open that in Caemlyn, why not the one at the Academy and at stedding Shangtai? Brandon likely totally misrepresented the battle around Cairhien RJ had planned. Elayne's retreat over the river to force the Shadowspawn to follow and buy time to rest, having the channelers take them out at leisure would have turned to disaster as the Shadow replied by sending more and more fresh armies through the PS, forcing Elayne to go defend Cairhien, ending up encircled as the Shadow sent more and more reinforcements, the whole plan to destroy the Shadowspawn there before they spread out through the central nations and brought them a new "Trolloc War" turning desperate and sour.
For that matter, why didn't the Shadow kept going with the sound strategy to use the PS/WG to open more and more battlefronts when they saw Elayne had taken their bait and committed a large army to destroy the Shadowspawn in Andor? As soon as the Light was embroiled in Andor, Kandor and Shienar, strike at Tear or Illian or Ebou Dar, for heaven sake! Shake the Seanchan's will to fight north by putting in play the Shadowspawn in the south. Leave them the choice to divide further or lose their cities one after the other. Rand foresaw this happening in the beginning, yet nothing happened.
We were also to believe the Shadow had plenty of infiltrated DF (who never struck!) but they never discovered those massively destructive dragons relied on the vital industry in Baerlon, very easy to destroy. They also never figured out the Light had stupidly set up a central hospital in Mayene, another target for Dreadlords to harass, at least to make it dangerous for the Light to stay there, force them to scatter in smaller groups or to spend precious time Traveling and setting up in different locations. But no... that ability of the Light to Heal officers and soldiers and bring them back fresh to battlefields the next day didn't count for Demandred, apparently.
Mat is a trickster and a genius, he noticed immediately Demandred's obsession bordering madness - a major weakness to exploit to keep him distracted from the battlefield, yet the obvious never even occurred to Mat (or to Rand, who also noticed the weakness) : give Demandred what he yelled for madly all day long, to force him and the Shadow to end the multiple battles and come to Mat's Last Stand at Merrilor: a false Dragon!
Instead of the big "War of Power" meets the Trolloc Wars RJ had set up to happen, Brandon gave us the "made for TV on a small and restricted budget" version, artificially depriving the Light of thousands of channelers, barely using the Shadow's real advantages. The Light ended up in the ropes way too soon, with the numbers of channelers they shouldn't have had until the betrayal of the Great Captains and the last stand at Merrilor.
We ended up with an often tedious early modern war, with touches of channeling thrown in.
We know the "four battlefronts" thing was outlined by RJ, and he discussed what he had in mind for the tactics, what battles he planned to get inspiration from etc. with his assistant Alan who was a fellow military history buff. In a way it's probably close to the great lines RJ had in mind, but Brandon rather mishandled the scale of the things.
It was also full of illogical stuff, like the Ajah fighting as units. Urghhh... that's cute and all Brandon, but that's wholly stupid... the White Ajah, very small and most often not even having warders, would have had to commit all its members to the field all the time driving itself to exhaustion and out of play in little time, while the Greens and Reds had enough staff to have rotations and all. Whatever happened to Egwene wanting to undermine the Ajah lines and the sisters understanding after the WT conflict and the Seanchan attack they had to work together? And whatever happened to Adelorna Bastine and the Green military hierarchy? They didn't do that for cuteness, it was an organization ready to come out as the Ajah's real chain of command during TG. The top Greens should have been all around Gareth Bryne and advising the Sitters overseeing his plans. But no, Aderlorna went MIA after an encounter with Egwene and must have been having tea in Saliesin with a pillowfriend or something...
The book had many qualities, some things Brandon really pulled off well, and whole aspects were good, but the military matters were rife with continuity errors and overall fairly tedious, and frustratingly way, way too focused on making Brandon's darling Androl shine. The rest was all too often a one-trick poney kind of things, the characters using impressive stuff but once. When he saw his efforts to bait Rand didn't work, you'd think Demandred would have started using his san'angreal to raise the stakes, etc.