If you try medium or low and drop the shadow and texture quality, does that give acceptable performance with better quality than very low?
Try setting the FPS cap in the options to 30, or something; a consistent rate may help the game seem a little smoother.
Try starting the game, Alt-Tab out, right click an open area of the task bar and select 'Start Task Manager', then in the Processes tab, right click EoCApp.exe, go into the 'Set Priority' menu and select something higher than 'Normal', and see if that helps any.
At 1280x800 with high settings and no shadows and setting EoCApp.exe to high I get around 35 frames, and when capped at 30 it's smooth enough to be acceptable to me. For now it is at least, I've only been walking around and scrolling in the very first area when testing. I'm not really picky. As long as the game is fun and playable then that is good enough for me. Hopefully everything will be fine when playing at these settings.
Is all that is going on here is me having a shitty video card? If that is the case then so be it, but if it could be something else then I would like to try to figure it out.
Since you have enough memory, disabling texture streaming can improve performance (it increases memory usage, which could potentially cause stability issues).
To do this, edit the graphicSettings.lsx file (in the '..\Documents\Larian Studios\Divinity Original Sin' folder) in Wordpad, or other text editor, and search for the term Stream, then change the one to a zero 2 lines below there.
<node id="ConfigEntry">
<attribute id="MapKey" value="TextureStreamingEnabled" type="22" />
<attribute id="Type" value="0" type="5" />
<attribute id="Value" value="1" type="4" />
</node>
This caused a crash after the initial loading screen. Is there anything else I can do to avoid this crash to see if this has any effect?