Since this is new, and the mod worked in prior versions, it is probably a bug of the engine.
Hmmm, interesting. The map i’m testing is a giant map. So i added another mod, that increases the maximum number of heroes, but without modifying the number of adventuring heroes. But: I found this bug on day 1, when i had 5 heroes (4 from map and 1 hired). So to what number does that limit the number of heroes?
I don’t know, I didn’t make experiments with this mod 
Well, i disable it, and now it works. So maybe it is intentional to limit number of heroes to less than 5 
Author said that Nullkiller AI plays the best with two heroes.
Well, may be. But for such big maps 2 heroes is a bad idea. 2 heroes is good for small maps.
And yes, the AI does not play very good here. So i gave the main enemy a big advantage. The human player (red) starts with 5 towns of 3 different type. The enemy (necromancers) has about 20 necro towns.
Grrr! Got the next crash. Game crashed on visiting a lighthouse.
I remember there was a problem that if only resources were left enabled, it was still impossible to hire more than two heroes
I can confirm it. This happened to me in game
I have similar problems with my mod. When dividing my mod into several submods, parts of my mod stopped working. After recombining them into a single mod without submods it worked again. Seems there is a problem with mods containing submods.
and I didn’t face it… There should be an exact way to reproduce I guess.
It may be because i’m using the latest unstable version. As far as i remember i did not have these problems using the 1.0 version.
I also experienced it. Investigating
Fix is on the way
Whow! You’re fast
Regarding resourceful AI mod, it just needs own config, which someone needs to introduce. Now it uses game-wide config to limit number of roaming heroes for all players