I may be wrong (can someone please confirm it?) but didn't the quest markers used to just point in the exact direction of the next quest stage, regardless of which zone it's in?You’ll experience a lot of situations where you are directed to the exit from a sub-zone, such as a city, rather than the actual target outside. When you have to enter a different zone, like this case, they are trying to tell you to go via Marbruk, but instead it got written as “in Marbruk”, possibly because the marker is there, to send you outside.
In some cases the exit indicated is not the bast one, especially when boats are involved.