Using a benchmark [1] to test for example, this helps a lot with performance when WINEDEBUG="err-d3d".
I also get a similar score up to a certain point at least, with this patch and without it, when not setting 'err-d3d', though I don't know if that is a good test on the enabled slowdown.
1. http://www.playonline.com/ff11eu/download/media/benchmark03.html?pageID=medi...