Neither Nassarius nor Marginella snails should spend time on your gorgonians. If it's spending time on them, it's probably eating them. I you can actually get a photo of the snail, I should be able to tell if it's one of the species that feeds on gorgonians or softies.
I tend to disagree about killing everything you can't ID. I usually vote to remove something if it is obviously eating something else you don't want eaten, and foregoing that, keeping it and trying to get an accurate ID on it.
Cheers,
Don |