Yeah, I understand your frustration. It's doubly so for us because none of this showed up in alpha testing, and we do have a fairly good-sized test group. But all this extreme and random instability was not seen before release. It seems like there may have been some recent changes that are at the root of some of these issues, so perhaps it was just a case of lack of time to test everything fully. But it will get sorted out, of that you can be sure.
As far as the trickiness of displacements as regards roughness and "out of control geometry", I think this is just one of the issues that has to be wrestled with. But we definitely want to make it easier to create these interesting, other-worldly terrains and shapes and development time will go into this in the future. In the meantime play around with the Compute Terrain/Compute Normal settings - Patch Size, Smoothing, etc. and you may get some interesting results. There is a good amount of power in there already and the end product will have even more.
I think Mojo now in 3rd edition has had some time to mature and really focus on exposing the engine's power. Over time I think we'll largely eclipse Mojo's capability, but I imagine there are things Mojo can do that TG2 might not be able to for a while.
- Oshyan