How to Reach Neriak Fourth Gate
Reaching Neriak Fourth Gate is extremely easy but extremely annoying. You have to go through Neriak, Neriak Commons, Neriak Third Gate and then to Neriak Fourth Gate. If you don't already know how to reach Neriak - that one's easy. You take the Neriak stone in PoK then travel north to Neriak!
The picture up top is Neriak to Neriak Commons. The picture below is Neriak Commons to Neriak Third Gate.
Finally the screenshot below is of the long run from Neriak Third Gate to Neriak Fourth Gate. Once you're in Neriak Fourth Gate you'll have to travel across the zone to reach the portal that'll take you to West Karana. I highly recommend you run over here and use the portal really quick that way you can get attuned for the zone.