minimizing can cause issues.

to give your cpu/gpu a break, you can adjust the frames per second while they are in the background. to do this, look at the setup/command editor... and the fields maxfpsbk and maxfps.

set maxfpsbk to 15 and
set maxfps to 40

you could lower the background on even further, it's up to you. 12 would be about 50% of normal movie fps... 15 would be 50% of normal TV fps.

basically, by setting the fps to 15 (or whatever) while in the background, wow.exe won't try to constantly render the screen... thereby saving cpu and gpu cycles for your foreground window.

let me know if that helps. good luck.