I never really payed attention to how exactly monsters scale with level, when they are player controlled (e.g. resoln's spiders and demons), but apparently they don't scale as they would do if they were just wandering monsters. At least that's what I got from modding the monsters one can get via wildland allies or other means.
For resoln's spiders this is apparently due to them being defined in the CoreUnits.xml and not in the CoreMonsterUnitTypes.xml, so they are treated in exactly the same way as normal units, i.e. just gaining a few HP, accuracy, etc. However dragons, trolls, ogres and other monsters you can get scale according to their level milestones in the CoreMonsterUnitTypes.xml if left in the outdoors, but not your domesticated versions. So your recruited trolls/ogres will never be as lethal as their free living brethren bred in the wild outdoors, which to me is a bummer as they are already pretty squishy for the stage of the game the tech becomes available.
What I did now was to add "Scaling Perks" for a few recruitable monsters and replaced the leveling milestones in the CoreMonsterUnitTypes.xml, but I am still wondering if this is just a bug and I could basically skip that part of modding.
Bug? Feature? Did I break something?