Height map strength problem

The displacement map in Blender can be used two ways:

1. As bump which does not move vertices but simulates surface movement (in a similar way to a normal map but only in one direction). It works but is limited in depth.

2. As real displacement.

You don't say which rendering engine you are using but if using Cycles you can use real displacement. In Cycles under the materials tab scroll down to the Setiings section and you will see Displacement which is defaulted to Bump only. Change this to  Displacement only and adjust the scale in the displacement node.  You need to ensure the mesh is subdivided first (and you could try adaptive subdivision)

Dave