Hunter's Mark is Bugged.

[Denkart]

ehm Vanish is supposed to dispell mark unfortunately, only thing that is vanish good at.

Yeah, except it is not supposed to.

''Removes effects that allow other players to see the rogue's location, such as Hunter's Mark and Mind Vision.''
http://wowwiki.wikia.com/wiki/Vanish

This is a vanilla realm... You need to use vanilla sources when searching for information. What you posted is applicable to how vanish currently works in retail. In vanilla, vanish did not remove Hunter's Mark. See the video posted earlier in this thread for proof.

[Gazpy]

Well Vanish effects say that Effect 11 is the removal of Snares and the alike, 7 is the Removal of Roots.
Both mind vision and Hunter's mark apply the same mod on the target meaning that you could not vanish out of the Mind vision aswell. I don't remember seeing this happen.
And the video is from 1.6-1.7 era? 1.12.1/2 mechanics are working otherwise.

On a Quest to find out what '(79) Sanctuary Value: 0' does: Check.

Actually easier than I though, It gives you complete immunity, Durr the name even suggested that. Now if that immunity does not impare with the stalker mod.

But indeed I agree why would this immunity dispell hunters mark and not the other debuffs, maybe the stalking mod is the key to that, but that will be harder to find as exact definition of dispell mechanics of that mod is quite unknown unless it's removed by it class immunity.