Even since the first RTW when I barely knew anything about history or weapons, I always thought the idea of fire arrows is kind of fishy, like why would they do more damage to the men or morale? An arrow burning is hardly gonna ignite your whole body, because it is a highly flamable material, wouldn't it damage or destroy the arrow? And why would it lower morale? That just doesn't make any sense to me.
Anyway fast forward 11 years later and historical TW still have fire arrows for some reason and not just that but in Attila they explicitly do most damage for some reason (Correct me if I am wrong).
If you don't understand me try Lindybeige: