When using a Blueprint Widget that has an image using a material in the User Interface Material Domain will not render when it's a newly created project in 4.11. However, if you were to copy a project that worked in 4.10 the widget would show up as intended.
For testing, I used a Galaxy S3 Mali, Nexus 5, and Galaxy S6 Mali per Jack Porter's suggestion.
For the widgets I used three types:
1. Create a new UE4 project
2. Create a new blueprint widget
3. add an image box to the widget
4. Apply a material using user interface material domain to the image box brush
5. In the Level BP use a create widge node with a return of Add to Viewport so that the BP renders when the game starts
6. Launch on or package for an android device.
Results: The Widgets do not render on screen on device, but show up in the viewport when PIE
Expected: The widgets will display on screen on the device
There's no existing public thread on this issue, so head over to Questions & Answers just mention UE-25703 in the post.