Not sure how many weapons this affects, but it is something that I have noticed with at least two of them. On both my and my wife’s computer, I have noticed that the greatsword “Pact Avenger” and the rifle “Super Hyperbeam Alpha” are not animated when viewed on my character in the world from my computer. However, when viewed in the character preview window or the hero screen, both are fully animated and appear to be working fine. I have seen the sword animated on other players (haven’t seen the gun yet). I made sure the Animation option in the video settings was set to high.
Not sure if this matters, but we’re both running NVIDIA cards… GTX470 and hers is a GTX580.