I have the below PC system:

CPU: Intel core i7 3820 3,6GHZ (OC at 4,2GHZ)
M/B: Asrock extreme 9 X79
RAM: Corsair 16 GB DDR 3 2144MHZ
HD: 
2XSSD 60GHZ in raid 0 (Operating system installed: Windows 8 PRO x64)
1xSSD OCZ Vertex 4 256GB (Age of conan client directory installed)
VGA: 2 X ATI XFX7970BE in crossfire mode
CASE: Coolermaster HAF942
PSU: Coolermaster 1000Watt
Monitor: Overlord Tempest X270OC 27'' working at WQHD 2560x1440 resolution with 100hz refresh rate.

ATI DRIVERS: 13.1 CATALYST (LATEST)

ASROCK DRIVERS: LATEST

My problem is very weird. I play the game with all details in max settings in DirectX 10 without FXAA and bloom.

First choise playing in fullscreen:

When I choose fullscreen resolution (2560x1440) ingame in the outside cities in open world I have 110 up to 170fps. Inside dungeons i see the extraordinary number of 360fps. When I arrived for example in the city of wild lands of Zelata fps dropped to 60. U are thinking the same as me. Very good performance. The opposite happens…...Even outside or inside cities I notice flickering shadows and the most important a very disturbing stutter on my screen like shaker like repeated Cuts in my screen on the left and on the right of my character. This makes the game unstable and unplayable.

Second choise playing in windowed fullscreen:

When I choose windowed fullscreen resolution (2560x1440) ingame the FPS reaches 70 up to 90 outside cities. When I arrived for example in the city of wild lands of Zelata fps dropped to 24. Every few seconds inside the city I show an updown fps from 24 to 75 like an elevator. Stuttering disappears and game is very smooth. My problem is that sometimes my game freezes for 2 or 3 seconds and I hear in this incident my graphic cards working from a high to very low speed.

My first solution is to play the game in fullscreen disabling shadows. Disabling shadows u are disabling godrays and the game looks very ungly like an MMO game with its age of 10 years old. 
My second solution is to play the game with one card disabling Crossfire but performance is not good.
This is rediculus and for god shake with this powerfull system can u play this game under these circumstances?? Answer is no at all.

All these days I read the posts and threads in the forum and I was looking also at google searching for this problem. All they said that the cause is the Dreamworld engine that doesn’t support Crossfire and SLI modes.

I would like to inform u also that I don’t have any problems playing other MMO and FPS games like GW2 or Dishonored. Fps is stable and games looked very smoothness and wonderfull.

All that we want and We would like is to play our favorite game…………

Υour opinion your advice is very valuable......

If you would have googled a little bit or searched for previous posts, crossfire doesn't work with 13.1! And if you managed to get it working, how well it works, is unknown.

I used the latest beta of catalyst drivers 13.2 version 5 and the game partially was resolved. Stuttering dissapeared game looks smoothness but the up down framerates stays like before and the flickering shadows also....maybe with the official unleash of 13.2 should solve them once for all...my problems solved at 50%.