When I was doing my Rogue quest to find this place I found these directions on the discussion of that quest here on Alla.
Quote:
Okay, here are directions as clear as I can make them.
Look at the Hillsbrad map. Start at the southernmost house shown in Tarren Mill. Directly east of that, across the river, is what looks like sort of a mesa. Go around the southern side of that, and then follow the east side to the north - up into the mountains. When you get to the top, look slightly to the east. You should see a path (it's not terribly obvious, but if you look you can tell it's a pretty even width ledge going up into the mountains). If you can't find it, move directly east from the top of the mesa shown on the map and follow that "wall" northward, and you'll find it. The path leads you straight to Ravenholdt.
Good luck!
Of course if you are Alliance, don't get too close to Tarren Mill. :)