I couldn't find the Dragonspine anywhere In Blade's Edge Mountains (don't have coords tho) I looked for ages with no sign. Found it in Zangarmarsh North of Serpents Lake - in a ring - on the hill right on the north edge of the zone (as described thanks). Was much easier to find.
I was able to get it at Friendly. Perhaps it's not longer acquirable once you hit Honored? He just has a blue exclamation point over his head for me ...
