Quote: Could the normal map do that impression?
Only to a certain degree. Normal maps can fake the angle of a surface, but they cannot create real depth. Any perceived depth details on a normal mapped surface are only illusions based on the shadowy areas created by the normal map.
A good practise is therefore to avoid 90° - holes in a surface that is supposed to be baked into a normal map. The map has nothing to "work with" in terms of angles except for the narrow border of the hole, since a 90° angle cannot be depicted in a normal map - so the result will always look like a very shallow hole no matter how deep it is in the highpoly.
The solution to this problem is to have a slope instead of a 90° angle - it will look much deeper as a result. In this case you could even make some sort of angled slits instead of plain holes... that might look really nice on the normal map. Like
this sorta.