Wanted to add my personal experience with farming for Salvager, it's probably not worth it unless you have a higher level running you through Maw of Souls, and my results with drops was similar to this comment on Wowhead:
https://www.wowhead.com/item=140217/boon-of-the-salvager#comments:id=2401826 . After questing through 2 zones, I've seen probably less than 5 salvaged armor drops, and only 1/5 of those drops contained Felslate x15. So, unless you're farming for Legion BoEs, it may just be better to focusing this energy on farming Leystone/Felslate, rather than farming for this shoulder chant