Aye - it confused me enough that I had to make a forum post :) Mostly what threw me off is that, even though when playing a "No Armor" faction, the tech tree showed that one can build a weaponsmith once one researches "Weapons of War". However, since the "Armor" tech is unavailable one can't upgrade a blacksmith to an armorer, and thus one can't obtain a weaponsmith.
That explains it (the second part) - I was playing a game with a "No Armor" faction, so the weapons of war tech was available, but not the armor tech (and thus not the armorer improvement). Thanks Heavenfall!
After researching Weapons of War I am unable to build the weaponsmith improvement. I have a level 5 fortress (and only one, so it wasn't inadvertently selected in a different fortress) with a forge and blacksmith built, but it isn't available. It looks like (from checking the hiergameon (sp?)) it was dropped off of the Forge-Blacksmith-Weaponsmith upgrade path.
I've noticed this in several games across several different versions. The AI consistently uses spells against Ophidians, lightning attacks against Crow Demons, and fire attacks against fire elementals. The AI both ignores units that it could damage with those attacks in order to target the immune units and neglects to use other attacks that could damage the unit. This problem is easily replicated by attacking a stack of air shrills with a young cro
I consistently have the same issue with Legendary Heroes, though not with any other games on Steam. Go into your Steam folder and rename your ClientRegistry.blob file ClientRegistryold.blob. This will force Steam to download a new ClientRegistry.blob file, and will hopefully fix the problem.