Mixed up things, now stuttering...

[TonyD]

I am a little confused by:

Originally Posted by Querer

... while the game runs smooth, the stutters seems to be comparable ...

but I can at least give you a place to start; these are my settings, and the game runs very smoothly (without stutters) with the following settings:
Cpu @ 4.2GHz
Resolution: 1920 x 1080
All graphic details set to ‘High’
AA, SSAO and A-E set to ‘Off’
VSYNC 'On' (but "Off' for benchmark)
Grass, shadows, roads ‘On’
I use SMAA instead of in-game AA – better quality and no performance loss.
‘Black Death’ benchmark: 44, 99, 7 fps (avg, max, min)

Your machine should run these settings at a higher frame rate than mine, so I would suggest turning one thing up from here at a time – maybe Terrain to ‘Original’ and then Buildings to ‘Unlimited’, and so on. At some point the stuttering may become apparent again, then just un-do the last setting that you changed.