Traveling was a great tactical advantage for the AS, but everyone knew the Seanchan would eventually learn it. But there's a simple reason why the Aes Sedai still have a huge tactical advantage over the Seanchan: AES SEDAI CAN LINK, THE SEANCHAN CANNOT.

Learning traveling will not aid the Seanchan much. At least a quarter of all damane won't be strong enough to even open a gateway. Some damane will be able to open a gateway, but not make one big enough for a person to travel through. The remaining damane who can make a gateway big enough to travel through will NOT raise the Seanchan to an even playing field. Even if you have a damane of Alivia's strength, at best, any single damane can make a gateway large enough for 3 or 4 people to go through at once. Most damane that can make a gateway large enough to travel through will only be able to make a gateway large enough for 1 or 2 people to go through at a time. Thus, the Seanchan learning how to travel will not really help them move large numbers of troops.

Once the Seanchan learn to travel, their best use of traveling will be for surgical strikes by sending through a dozen or so sul'dam / damane pairs with an honor guard and hitting the enemy flanks. The mass of Seanchan soldiers will have to move the old fashioned way.

Compare what the Seanchan have (or will shortly have) with what the AS have. The AS can also travel, but because the AS can link, they can open 100 pace wide gateways and move tens of thousands of troops with ease. Imagine 6 sets of 13 women linked. That's 6 different gateways, each one 100 paces wide. The AS could move their entire army in less than an hour if they organized correctly and practiced the maneuvers to perfect it. In fact, considering Egwene has access to a couple thousand channelers, she could probably form a hundred companies of 13 AS each and make 100 gateways, each one 100 paces wide. She could move her entire army in 5 minutes.

So, to properly exploit traveling, the most important thing is the ability to link. The Seanchan will be limited to using traveling for surgical strikes and not much else.

The AS still have the main advantage. The question is, is Gareth Bryne smart enough to realize this? I doubt Captain Chubain is smart enough. Hopefully Gareth Bryne will take over command of all of Tar Valon's army now that Egwene is in control. Hopefully Gareth Bryne will also realize the potential that traveling has and hopefully he's smart enough to have his troops drilling and practicing moving by traveling on a regular basis. A good army commander has his troops practice the routine over and over again because the first time you don't realize what problems will crop up, so you practice it until you work out all the problems.