Edited for spoilers
In 4.4 it's explained that when they razed Dalmasca the Empire shot themselves in the foot by destroying an important refueling station for their armies, making it diffiult to fly around the burn to get to Doma. And by putting up a barrier around The Burn, it because impossible for the Empire to just fly over it apparantly, guess the barrier is too high up to just fly over? So Doma seems relatiely safe from counter attacks for now.
Ala Mhigo as I understand it actually held the Empire back for a long time, and was only conquered because Gaius took advantage of a civil war. (I also hear that he may have had a hand in starting said civil war but I'm not 100% on that.)
With the stage set for an attack on Ala Mhigo in 4.5, I really hope it gets one last moment in the spotlight and some more development before we cross the land bridge to Garlemald in 5.0. The did leave the Fordola plot thread hanging, as well as Ilberd's two cohorts who were captured off screen. A big battle could be one last opportunity to make the expansion live up to its name too.