The shortest path is through the wetlands and loch modan, but I would recommend coming from STV. It will take longer and may result in many deaths, but you will get all the flight points for the future (and you gotta get them sometime).
First go to the zeppelin station and get the flight path, and pick up the one in booty bay at your leisure...
From the zeppelin station, run north on the road until you get to duskwood. Then run along the mountains on the south side. You can actually get pretty far up on the mountains if you go up the ridge immediately after crossing the bridge into duskwood (which avoids a lot of mobs). Follow the mountains around until you get to the road into Deadwind Pass, and go through to the Swamp of Sorrows. Get the flight point there and go back through Deadwind Pass.
Turn right as soon as you get to Duskwood again and go over the mountains through the waterfall to avoid the town and head north along the road into Redridge Mountains. Go straight over the hill and around the western edge of the lake. Go up into the mountains (to avoid the town) and run through the mobs camps. Pick up the road into Searing Gorge and run straight to Flame Crest to get the flight point.
Then run into Black Rock Mountain. Run around the ramp, and out the exit into the burning steps. When you get killed, rez at Thorium Point and save time. If you live, take the road around the eastern edge of the burning cauldron, and run along the north side to Thorium Point to get the flight path. Then run back along the north edge and find the pass into the badlands in the eastern mountains. The road goes to the alliance-only gate in the north east corner, and the pass is a little ways south of there, but there is no "road", just a pass you have to look for.
On the other side of the pass, turn left and Khargath is right there with the flight point. For a total time of about an hour running like a madman you will get all the Horde flight paths in the southern continent and never have to make the trip again.