With my WL I have two quests guiding me to Malaka'Jin in Stonertalon. Have been in Grgrimmar ans in XRoads as well, both times I should go via Thunderbluff. But there is no way from TB to Stonetalon through the mountains or at least I don't know any path.

 Are you sure the travel routing feature of Carbonite is not telling you to use flight paths? You can tell when it is because the text under the HUD arrow will say "fly" somewhere in the sentence.

And the arrows will be yellow instead of white if it is a flight path.

Moved the thread to the quest forum.