Not yet, I just finished mission 6 yesterday and it was by far the hardest thing since I started the game lol.
So it's the one where you have to capture 3 cities on this small island-y map. The way I played it I went past them at first because I figured, if the neutrals are holding them I can just lvl up and the comp won't be able to take them then I'll just come back to them when I'm finished. So I keep exploring and find the comp's capital clear his heroes and there is some defender of faith quest objective party. So I kill it and then I've cleared all the interesting parties on the map. Then I go back and start capturing the cities and this is when the shit hit the fan.
Basically exactly two days after a city is captured some stupid trigger goes off and 3 FULL parties of lvl3 units (paladins,imperial assassins, inquisitors, healers etc.) spawn and move within attack range of the said city. And these quest towns are quite far apart - one of them is 4 full turns away from the other two who are 3 days of travel apart. So because the scripted constantly spawning parties are so strong there was no way to hold those shitty towns even at max tier with only lvl 1 units, my main didn't have time to run around and there were basically no neutral parties left on the map for xp.
So what I had to do was leave all my high level units in the capital, then buy two griffins and an archer and just grind XP from the stupid perma respawn parties until they levelled up to skylords. Then I left them in a hero near the capital and did this AGAIN. After which those parties in tier 5 towns with some debuffs on the attacking parties finally managed to hold the bloody cities. Mission took something like 150 days...
I'm almost 99% sure that the map scripts bugged out since I killed the merchant leader dude first and those guys are not meant to spawn infinitely... And I could not clear the capital to break the AI chain because there were no armor consumables in the entire level
