You will get a speed increase when rendering in "Preview" mode instead of "Final Render". There are also settings for super-sampling and shadow quality when in "Final" mode. If your preview is looking good to you already, then you might just want to render in preview mode.

The textures and other stuff using VRAM generally have a far greater effect on your speed than the poly-count.

I did not mention how many times iClone crashed on me. All during test rendering or just loading a project. Every time I close iClone, I am scared, that I would not be able to open my project again. Computer restart, clearing iClone temp folder and closing all other apps helped though.
Now back to rendering. I was also wondering why is it playing live 60fps is fine but rendering is just 0.7 fps (1080p) (I would be a happy camper, if I had 7fps as justaviking mentioned). Should probably do more testing with rendering in "preview" mode and compare the quality and speed. I've achieved just a little better speed by collecting a clip into iMotion plus file, removing animation and loading it back for the main character. But I suspect countless trees are the real bottleneck here (as sw00000p suggested). Would need to carefully plan the scene next time. And yes, graphics card is due for an upgrade too. 
Thank you all for suggestions :exclamationmark:

Not sure why though

Because Iclone 5 has only 4 lights casting shadow. Iclone 6 is build on infinite lights casting shadow. 
For those thinking that UDK 4 is far better as iclone 6 , do the test by importing all your scene and relight as in Iclone and try to render.... You'll be very surprise.

Would need to carefully plan the scene next time

This is exactly how you must think to speedup your workflow. It's like making movie like Maya but with a pipeline of game engine.
Or you can hide all the unseen props depending of your camera view.

That made me thinking about shadows for my trees. I cannot test now as it's rendering. But If I remove all shadows from trees and then add only for those close to the main stage, where it is actually can be seen. Should that improve performance? 

Should that improve performance?

Awesome mtakerkart!

Also, if you have multiple lights in an outdoor daylight scene, you probably only want one of them to cast shadows. I think your better off rendering with shadows, but being frugal with them.

OK, I am puzzled even more now.

Render: 1080P, MP4, 200 frames test (actual render of 100 frames @ 30 fps), "Preview" mode render.

Saved project under different name and started taking stuff out of the project while testing rendering speed.

Found that most weighted items were sky and terrain. Fine, after totally cleaning up the scene, shutting down all visual and setting project preferences to default, the render speed was.. only 5fps.
However, if I start a new project and do the same rendering test, the speed is... 10fps.

And nothing I could do to match the render speed of cleaned up project to freshly created...


Update: At any rate, "managing" shadows has saved me a few hours for final rendering of the project. 2.5 hours projected @ 1080p for 3.5 min clip.

Rendering in PREVIEW mode is not the same as the rendering in the PREVIEW window.  The PREVIEW WINDOW is much much faster, and the results are WYSIWYG, so there's no guessing what your results will be. Rendering in PREVIEW mode is not WYSIWYG from my experience.