Which version of Vue? 5 or Infinte? If Infinite, use the function output observer to get an idea of the results of your experiences. I'm no expert on proc terrains, but what I usually do, is start with a simple perlin gradient fractal, connect its origin to a turbulence, try different ones, and combine this to another fractal, this time an altitude voronoi. Then try different blending methods. I found that substract often yields to good results.