I have exactly the same problem. I'm playing Final Fantasy XI: ultimate collection via Steam and since I started playing two months ago I can't see any effect while attacking with a weapon. I checked the drivers and everything but, as Asura_Daimaoh says, I think it could be something related to the graphics configuration. In my case, when fighting, I can see every game effect (even casting spells) except when using melee attacks! The spell performance is seen (I mean the bubbles when casting white magic, for example), but no spell, attack or technique effect is shown.
What can I do to solve this problem? It's really annoying not fully enjoy the game.

Thank you in advance