After countless hours of debate, research, etc, I sadly consider myself an expert on the subject. I'd say it really boils down to your DM understanding the poorly-written rules and then being fair in his/her assessment of what is "appropriate."
For instance, the above power example states "you must have cover or concealment from all enemies" which just isn't true. Nothing in the PHB states this. You merely need cover/concealment against any particular creature. Again, the example is a room full of monsters where half of them can see in the dark and the half can't.
The DM ruling on "appropriateness" comes into play when the DM decides that the creatures with dark vision have some way of effectively warning or communicating:
A) Exactly where someone is
or
B) The fact that someone is there, but not their exact location.
I.E.
A dark room where you have "guard dogs" that can see in the dark. Their barks might warn their masters of something being wrong when a stealthed player enters the room. However, the dogs cannot effectively tell their masters, "Oh, he is 2 squares to the right and 1 square ahead of the main doorway."
I think the rules work. But I agree they are worded pretty poorly, can be very confusing, are broken up into too many areas that must be re-compiled to derive a clear meaning, dont' do a good enough job of describing what happens when an already noticed player or a player who is partially visible successfully stealths, etc.