Ok,
so i took some time to put together that scene. I have to make clear again that you should
never ever just render the converted scene. It will never work, it can not possibly work. It is just an aid to make conversion process easier... but just about 20-25% easier... you are going to use completely different engine, so it is never going to work out of the box.
I have created all the materials from scratch, and i did not try to match them 1:1, i just made some materials like i would in a regular scene, so i am not performing test on a simple clay render. Also, never light your scene with giant sphere, just put environment map where it belongs, into environment slot.
And if you are making emissive materials, then make sure just emission component of material is enabled. Rest of them, including diffuse, should be disabled.
Use hybrid glass mode whenever possible. Use solid only when you can afford it... never for large glass elements, but for small things, like glass statue on the table of a room lit by large window...
Try to avoid fakes as much as possible, and never try to make lighting complex and then throw it on renderer expecting it will handle it. It never will. The point is to make scene as easy for renderer as possible without sacrificing too much quality. Most of the time it is not about making supercorrect render, but about finishing all renders comfortably before deadline.
If you are irresponsible with your lighting and shading, you will never get reasonable rendertimes in any renderer. Be it Corona, Vray, Mental Ray or Arnold... That being said, Vray is sometimes quite forgiving when it comes to irresponsible shading and lighting, but it is still not nearly bulletproof.
So, here is my test:
It took 30 minutes on my older i7 870... so on something like 990X, it should take no longer than 20 minutes, at this resolution.
I am also attaching post processed version, to show you can always fine tune image in post, instead of trying to get it right out of the renderer while messing your render settings up in the process.
You can PM me your email adress (Nehale only, no-one else :P), and i will mail you the scene so you can take look at materials, lights and render settings yourself.
