elaborate, I want a good laugh.
Most of it was scripted
iirc. Consider though that I have no fookin' idea what I'm talking about, cannot into software
That's not to diminish the value in SCS, but its source code is public on github, and anyone can see SCS consists of (lots of) behavior scripts, the kind which first were made available by BioWare with BGII.
That's why BG1 never had a mod like SCS, but BG1:EE is supported by SCS.
For what I mean under "AI", see for example this:
http://battlebrothersgame.com/dev-blog-27-ai-battle-brothers-part-1/ and the GDC presentation they reference.
BTW, from superficially looking at what enemies are doing in WotR, it looks like they either attack you with default attack, use spells and abilities in a scripted sequence, or cast spells at predetermined coordinates - like that baphomet cultist in the first quarter of Market Square who always casts color spray in the same direction, sometimes hitting his own guys. They still have a lot of scripting to do until they reach SCS level if they ever reach it, and would never reach Battle Brothers' level.
They also rarely switch targets. The only reliable instance when they switch targets, in my experience, is if they are moving towards a character to attack in melee, but are intercepted by another character which attacks them in melee. Then they stop and fight the one who attacks them.