Did you fight during daytime or nighttime? When it comes to archers it's a feature implemented that during nighttime archers can't fire very far. Reason: Without lightsources, you can't really see jack **** at night.. you would know, if you've lived in the wilderness without electricity.
When it comes to banditcamps, they are meant to have lightsources, campfires etc, hence you can see the enemy. Archers can fire.
When it comes to archers fire over the whole map, it all comes down to the speed of the arrow and how they coded falloff speed etc, the math behind etc, so it would not be the horsearchers that's buggy, but the math behind it and the bows they're using etc.