As the SLI was working perfectly before upgrading to 285.62, I suggest going back to 280.26 (at least for diagnostic purpose). If it works without problem, then this eliminates any possibility of a hardware fault.
The worst case scenario is that you will have to use this 280.26 instead of the 285.62. I do not think you cannot play BF3 and Batman Arkham City. The older driver is not optimized but it should still allow you to play through those games.
BTW, when you did the driver upgrade, how did you do it? What procedure did you use?
When I install new drivers I uninstall the old one from add/remove programs then reboot in safe mode and wipe anything remaining with driversweeper. Then i reboot again normally and install the new drivers.