Crossfire Radeon User here:
System:
Intel Core i7 2600k @ 4.3Ghz
2xRadeon HD 7970 @ 1050/1525 @ 1.2v
Windows 8 64bit
Catalyst 13.6 Beta2
FFXIV Settings:
PC-Maximum
2560x1440
I uninstalled 13.8 Beta2 due to reasons with other games. I found no issues returning to 13.6 Beta2. I get 60-70% Load on both cards, and >50 FPS in most areas (of course areas with lots of players I become CPU bottle-necked so FPS drops into the upper 30s.)
The best CFX method I found is Optimize 1x1, AFR-Friendly works too but I found it had more flickering and Default is almost useless.
Create a profile for FFIX:
Right click your desktop
Click AMD Catalyst Control Center
Click Gaming > 3D Application Settings
In the new window click the +Add Buton
In the new window find your "ffxiv.exe" it will vary depending where you installed it
Once you got the profile made, on the very bottom you will see the option: CrossfireX Mode. Select "Optimize 1x1"
Save Profile, Launch game (make sure it is in Fullscreen, CFX only works properly in Full screen.)
Enjoy decent GPU Load and Frame Rate.
Images to help:
AMD CCC Profile:
http://i.imgur.com/gls3G2b.png
FFXIV no CPU Bottleneck:
http://i.imgur.com/aJUIXaO.jpg
FFXIV CPU Bottleneck:
http://i.imgur.com/9nXvDH6.jpg
Hope this helps the Radeon users. If you use Catalyst 13.8 Beta2 you'll have the Frame Pacing Option, On/Off shouldn't make a difference but then again I had to stop using that driver since it doesn't work with some of my games.