There's a lot of potential in all the prime cards, so I wouldn't dust any of them. Dusting legendaries that aren't completely useless; like gruel or hogger etc, isn't a good idea as the dust return is only 400 if you wait about a week and get a pack a day you'll get the dust anyway.
Right now in the meta its not that great. However...
I feel like maybe theyre going in a different direction with Shaman in this expansion. And I have a feeling theyre gravitating toward something else in the future and then the card might be viable or even a downright necessity in Shaman.
Hearthstone has always kind of been like that. They introduce a few cards and theyre not quite good, but then another expansion or two come out and all of a sudden a new archetype emerges using older stuff. Kind of like Spell only Hunter or Deathrattle/Thief Rogue in the past. Just some examples off the top of my head.
If you desperately need dust now and aren't a Shaman main then you could dust it. Otherwise, I'd hold onto it.