this is just a guess.. but it seems that nearly every quest to find someone in the vale ends up near the dreadoth temple. My first guess would be to go to the temple, turn east til you hit the mountains, then turn south.
Yes, Maps are helpful There are a number of maps you can find in this forum.. try running a search on maps.. At least one of them have a small map of the vale included.
I did the Stargazer Quest and honestly can't remember where the hell I found Okula. I just went up one side and down the other. I do not think he was near the temple though. Oh, and the War Witch quest was near the middle of the Vale, just so you know.