One drawback of the heightfield method is very little control over noise on steep slopes. Given the richly textured vertical walls of mesas, this was a problem.
The solution I found was to mask out just the cliffs in the heightfield, convert it to geometry, deform it further, then bring it in to the scene along with the landscape. This way, most of the heavy lifting is done by the landscape HDA, but you don’t lose the cliffs. For this scene, I also created materials with substance designer for different parts of the landscape which were masked out.
Rendered in Unreal 4.25