I know it's not supported yet, and I know those that force SLI or Crossfire as well know it's not supported yet.
Maybe I'm not alone with the glitches. First off, You might be better turning it off, I'm sure not everyone is the same.
With my experience using Crossfire, I get rapid flickering with lit objects, it can be the ground or the sky, and even in player/npc names. I even notice screen tearing quite often during game play(probably due to no V-Sync). However, after turning off Crossfire and running off 1 card, the flickering goes away, tearing stops, and my FPS average is even improved by 10-15 points.
If it merits anything, I run:
2 XFX Radeon HD 5770s CrossFired
6Gigz DDR3 Corsair XMS3
and FFXIV on a Samsung 120GB SSD
Everything stock clocks.
Crossfire Active 28-35FPS
Crossfire Inactive 35-50FPS
So ya, if anyone is having similar issues, that could be your problem.