Made for Patch 6 - Hotfix 19, Working with Hotfix 25, Most likely works with previous patches(Proceed carefully, but it's just a mesh replacement; no code was touched and it should be compatible as a mesh replacement for previous patches.)
Sooo, it turns out Astarion's grinching (said completely affectionately, btw) is actually a graphical bug! Lowering your game's graphics settings to Medium can help, but so can this mod (to an extent). ~~This mod is a replacement head model for Astarion, that fixes some issues with shadows/textures loading incorrectly (making him occasionally look like a certain Dr. Seuss character).

For a basic explanation of how it works, it turns out Astarion's original head model is missing some LODs other head models have, which also affects the export order for the model. I'm guessing this may be causing shadows/textures to be loaded incorrectly on him. I'll be transparent, I don't fully understand the mechanics of Why this fixes it, but adding in those missing LODs does seem to get shadows to load better on him, so that's what this mod does.~~
vyrelis and I have now figured out how this fix works—check the top sticked post in the comments for details!

If you don't want to read all that, though:

tl;dr: this mod incorporates the same fix for his animations the vanilla game does, by making his model switch to using the medium animation LOD setting. However, this mod lets you use that fix without affecting other characters, and also lets him keep his original wrinkle map, as long as animation level of detail is still set to high in graphics settings.

Basically, this is already a Larian fix, with all Larian animations—this just lets you use it with a couple extra benefits!

You can see a comparison between the original and replacement meshes here:

It's not a perfect fix for his general...grinchiness (I think some of the issues with his funky expressions may be due to them just, not updating his early access animations for his new model, which I am not going to try to fix) but it does seem to help. Also honestly he just kinda looks like that tbh! Sometimes you just have to love your hag the way he is. While...also making sure his model is functioning properly......Hm. I don't think that's how the saying goes (or how any saying goes), but it's fine.

**This mod makes no changes to his model beyond adding LODs.**Note: the LODs I added for his teeth and eyes are duplicates of the original models for them, just in case the reason those LODs are missing was to prevent them from looking funky on lower graphics settings.

This mod is compatible with other visual changes for Astarion, like No Abs For Companions, with the exception of other head replacements. Mods that edit haircolor/eyecolor/etc are also compatible.

The file for his original model can be found here:

Generated\Public\Shared\Assets\Characters\_Anims\Elves\_Male\Resources\ELF_M_NKD_Head_Astarion.GR2

If you run into a visual change that's not compatible with this mod, let me know!

Install by dragging the Generated folder in the .zip file into your BG3 Data folder, which can be found here:

\SteamLibrary\steamapps\common\Baldurs Gate 3\Data\

The model can be safely removed at any time, even mid-playthrough, so you can re-grinch your vampire at any time with no worries.

Thank you so much to Padme4000 for the Blender Addons! The Create LODs addon is a lifesaver. And thank you again to vyrelis for helping me figure out how this fix really works!!!

As always, let me know if you have any issues, and enjoy!!

(By the way, if you like my work, tips are welcome!! You can do so through my ko-fi here: https://ko-fi.com/herotune

It's the same ko-fi I use for my art, but I'll never paywall my mods. Thanks for taking a look, if you do!!)