I don't know... I think it's not a difficult mission... It can be completed on the second attempt with the first Fortress hero... Compared to the mission for Agrael against Gilraen or the "Emerald" mission - it's nothing, IMHO.
The mission where you have to defeat Gilraen is certainly difficult, but not as large-scale. I replayed it five times until I achieved a positive result. And here, even though I passed it on the first try, I spent a lot of nerves, and I've never reloaded so many times! And the mission with the Emerald faction was very easy for me.
