I was near the end of a game with a ranger, and entered a Fang base at character level 15, the Fang clan was levels 18-21. They declared war when I introduced them to my allies, a big fight started, and I noticed some pretty severe bugs.
- Ranged NPCs (casters, in this case) near buildings would stop at the corner and cast spells at the wall while I dealt with their melee fighters.
- Even worse, as long as I could keep a tree between myself and a caster, they'd keep casting at the tree, while my arrows went straight through. Not only were they not realizing they were just hitting the tree, my arrows probably shouldn't have been passing through it.
With these bugs, a ranger can kill entire bases of casters effortlessly.
Also, the war started because of another possible bug - relations between NPC clans that have never met seem to decay as if they were in contact. This was late in the game - they hated each other before even meeting.