Sorry guys but I really don’t get it. You are comparing some apples with bananas. I won’t say light mass is perfect but it does a good job for what it is intended to do. It looks like a misunderstanding of technology. You can’t go and use an engine that is made for real time rendering while moving around in a scene, creating an image in a fraction of a second, and expect the same results as an engine which is made to render one still image in minutes or hours.
Once vray or corona are able to render in real time I will support your demands. But until then just try to get your light maps right and it will be reasonably fine. It will never look like a vray or corona rendered image. Something that is done with unlimited time and unlimited resources (memory and geometry detail).
Look at it that way: with vray or corona you try to take a photograph. In unreal you are more like a painter. You can do realistic paintings but they will always be paintings and sometimes you need to hide a few things. If your painting is consistent then the viewer will believe it. If there are spots of super high detail next to something very undefined then your painting won’t work. I know it can be frustrating to not get the result you expect. But if you understand what unreal 4 can do and what it cannot do then you can get some really amazing results.