Although it is a long time since, I am still having the tearing problem when in fast disc mode despite updating firmware and drivers for my cards. Recently I used a third rental machine in which I installed a Raptor and the tearing occured there as well.
On my machines I am now running a 4 raptor striped raid and in fast disk mode I can run 5 to 6 layers at full frame rate but in slow mode it is back down to 2 solid layers at 25 fps.
I have single Raptors set up as Catalyst System only drives with basic installs and no other applications. I then run my external raids or an internal content drive.
apple seemed to have changed something in the graphics architecture after 10.3.5
i hung around seeing if it got changed again.
10.3.3 is the best solution for now.