Shredder vs. Saberon (Alliance)

In order to complete this you need to find your way up on the mountain.

The easiest path is just north of the cave where you picked up the quest. (To the right as you exit the cave)

Simply click the vines to cut through them and as you go through the NPC will meet up with you to complete the quest.

Do not get in your shredder, then run up to clear the vines; clicking on the vines will not work if you're in your shredder, nor will your abilities clear them.

You need to be on foot (or mount), click the vines, and you will automatically enter your shredder and clear them.

Path entrance:
/way 54.3, 46.4