I am not sure where to post this, but my GF is playing on a MAC and I have realized that mobs and NPCs do not have weapons, in fact the animation for the attack is as if they are using fists, so it's not just that the weapon model is missing.
To be clear, she can see the weapons of players and herself, but no NPC's or mob's weapons.
We have the Wratch of the Lich King expansion and I am playing on Windows version with no issues.