Well this would take some time to fully debug but there are a few things I immediately do see.
First off, sound being on puts amazing demands on your machine, if you can live without it, I suggest you turn sound off. There are a few fights, most conspicuously Phara Dar, where sounds provide important cues. For such fights you can turn on a portion. It has also been suggested that you use an empty sound file just to make sure sound is truly and completely dead (as in the Wicked Witch of the North in Wizard of Oz). Please look at this forum:
viewtopic.php?f=204&t=9195Second, you could make sure your multiple cores are used better with CPUAFFINITY settings. You should also make sure that none of your CPUs are parked in the interest of low energy consumption. Both of these are mentioned in the above forum and elsewhere.
Stick figures are pretty boring to look at but hmmm, they really do take the edge off resource demands on the GPU. You can imagine a flashy bit of armor moving during a fight and the wearer moving about and how all the angles and etc have to be calculated to make the armor look right to all players...
I'm glad things have improved, but undoubtedly tweaks could make things still better.