One other thought,
Was this a bug fixed at some point in revision history?
Im not sure if im playing the most current version.
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OK - this is weird - edit.
I got to the oasis eventually. There is more that needs to be done other than freeing the Vasir before the road opens and you can make enough moves before dying in the desert to reach it.
Im not sure if these extra steps were intended (not listing here for spoiler purposes), but if you want to shoot me a private message, I can explain further.