Quote Originally Posted by mbox_bob View Post
I had a play around with WoW today, and found that if I lowered the graphic details from High to Good on just about all the Environment and Effects settings, this actually increased CPU usage from around 10% to 16% for the one game I was using to test (this is on an i3770k at stock). This was only in the starter area, without all the visuals you get in a boss fight, but I think it was a reasonable test.
I'm only guessing but I figure the implementation by Blizzard is assuming that people reduce these options because their GPU is not powerful enough, so they offload processing onto the CPU along with reducing some of the bling.
I concur. More specifically, with reduced visual fidelity it increases framerate requiring more CPU to render the additional frames regardless of non-CPU considerations. As with you, it's just a suspicion but it makes sense.