Not sure how random it is. There have been other posts about it and I have had it happen to me as well. There are no visual weapon effects for the vasari after a certain amount of time. They are there in the beginning and then just click off for some reason later.
Thought I would add my 2 cents. I lose weapon and explosion effects playing as the Vasari as well. As Sunofvich was saying, it just randomly turns off. I have noticed too that with all of the races, that sometimes the dialogue and special effects noises will turn on and off. Perhaps I'm just being blasted by the music and don't notice it, but whenever I click on the sounds option from the menu and then back into the game, the dialogue resumes. I'll be keeping an eye on that more. (and an ear)
