Material Tessellation is no longer working in 4.11 Preview 2, 3, or 4. It is also no currently working in 4.12 Main.
Working: 4.10.2 - CL-2818068
Not Working: Tested in Dev-Release CL-2824708 
Not Working: Releases-4.11 CL-2822657
Not Working: Dev-Main CL-2845412 
1. Open UE4 
2. Setup basic Tessellation Material
3. Apply to mesh in scene or use the material editor view
4. Change the View mode to be Wireframe
Regression: Yes
Results: Tessellation is not working.
Expected: Tessellation should work
Head over to the existing Questions & Answers thread and let us know what's up.
| 0 | 
| Component | UE - Graphics Features | 
|---|---|
| Affects Versions | 4.11, 4.12 | 
| Target Fix | 4.11 | 
| Created | Jan 12, 2016 | 
|---|---|
| Resolved | Feb 24, 2016 | 
| Updated | May 2, 2018 |