Graphic cards : 2 x RX 480's
Blender 2.8 beta v.2.80.74
Radeon ProRender Addon AMD 2.0.94
When I enable 2 graphic cards at the same time the render is slower than just enabling 1 card.
Render is also very slow and took 1 hour 20 minutes. I think code needs to be optimized.
Very slow compared to Cycles renderer.
As your other post... Tiled Rendering is the culprit here. Turn it off. I'm not sure multiple GPUs are scaling very well at the moment, they're not in my testing, but Tiled Rendering is a recently added feature and definitely has major performance issues.
Your rendered image is really good though
Join us on the Discord server if you're not there already so you can post Work in Progress renders of the scene. The community would love to see them. It's looking like an awesome scene.