Half baked solution is the best solution at the moment for open world games made in UE4.
We choose this solution after almost 1.5 year of studying and researching.
Cascade shadow lighting is unstable in certain situations, for example in our interior the external directional light is not culled correctly and we still have Shadow Depths killing our framerate.
If you optimize your assets with all the tool the engine gives, you can achieve 60 fps on a gtx 970 with some nice graphics.
Unreal Engine is not 100% ready for open world games, but it’s near to it every day and every update that comes to us, so let’s just have patience and remember that it’s free and open source, however it doesn’t mean that answers like “do it yourself” are acceptable, imho.