sorry for the late reply, been rather busy these last few days.
1. What "blind flash" technique are you referring to?
2. If your having throttle issues your FPS, (or Frames Per Second) will drop and the game will visually stutter on the screen and basically become unplayable till the card cools down (usually takes a few seconds). This isn't a common occurance with the 560m though as it run's a lot cooler than the 580m. As to your FPS issues with wow, have you tried upgrading your drivers? that might help. You could also try Overclocking a bit and seeing if that helps out at all.
3. Well the 680m would more than double your GPU speed, but like you said the card is very expensive. This 6990m I got rather cheep has been running great other than the usual crappy AMD drivers. More than double the FPS of my old 460m. Hope some of this helps.