Where exactly do you place troops when your enemy can not only scout your locations via Traveling, but also mass deploy troops in the same way? It's possible Demandred needs a corp of highly mobile troops to avoid being flanked. The use of Gateways in battle can go way beyond simply moving troops from point A to point B. it's the equivalent to introducing cavalry or chariots against unmounted troops. Only a matter of time before the Seanchan or Matt (or Matt with the Seanchan) think about rapid troop deployments, communications, or some other interesting use for Gateways on the battlefield. Imagine the dragons coupled with the mobility of Gateways.