One of the things I tell people to try, since I was told the same, is:
When in game, go to Options->Graphics->Details.
There's "Fps cap" value. Lower it. I've it at 25, and the game looks Ok to me.
It's true that I run it windowed, on 800x600 resolution, and that I do nothing risky with it (attack mobs with combo fatalities or read a book inside a library) but so far I experienced a great cpu usage when playing the game, and no visual loss (that is, you don't see lack of "image refreshing")
If that is of use for you, I might very well suggest changing the default settings of the game, to a lower fps cap by default, so "better performance" is experienced by players, right out of the box.
And... now that I look at that fps cap number box, I'd ask too for the ability to directly type there the desired number, instead of being forced to use the slider.
And I also seem to recall Santa forgetting some of the presents he owed me...