How to Disable or Remove an spell's visual?

for a week now i have noticed that sometimes when i use barkskin or bone armor in raids my game either freezes for a few second or crashes & it only happens in 25man raids specially in the more cpu/ram heavy demanding fights like marrowgar is there any way to disable or remove an spell's visual?

I am not sure; probably you would have to edit some dbc file. But there's no guarantee that this is occurring because of the spell visual. It's probably an issue with one of your addons.