You are not pointing at a visible field in your screenshot so it's hard to tell if it's working. Dark vision "allows you to see through creeping darkness out to a radius of x". The fields still appear as "dark" but if you hover over them, the games states "in sight" when you can see a field.
Example: There are 2 fields of darkness left to you. You then enter it.
Without dark visions: you can't see whats outside on the left side of the remaining field of darkness but what's right of you.
With dark visions: you can see out
trough the remaining field of darkness up to a radius of x.
Note that you can always see out of the darkness, when you are standing directly at the border of it, even without dark vision but only
trough fields of darkness with the talent.
Note the visibility of the human farmer to the left.
http://steamcommunity.com/sharedfiles/f ... =316160890 without dark vision
http://steamcommunity.com/sharedfiles/f ... =316160829 with dark vision
Edit: Clarification: It works exactly like a seperate "infravison" which only works for creeping darkness. You only see units, nothing else. Up to a range of radius noted.
So on level 6.5 you have "infravison" 8 trough creepingdarkness (so all your skills work at max range if you got a darkness wall in front of you). You still have to be able to see the unit by other means (e.g. if its on an unlit tile 7 range away and you only got heightend senses range 4, you still don't see it).
I hope this clarifies how it's working. It's just a sperate kind of infravision that only works for seeing trough creeping darkness.