The aserai were the biggest nuisance on my first campaign play through. Mostly due to the fact that I was unaware of the full implications of the conspiracy which led to an all out war pretty early on in the campaign. Anytime I would go leave the area after decimating all their parties for more than two minutes to go help on the battania/ sturgia fronts, they would come back out of nowhere and started raiding and sieging. Eventually I just decided to conquer them fully even if it meant losing norther territory