Last week I played for few hours Diablo and I sow that they changed the pack files format. So after a fast search in the net I found this: http://www.zezula.net/en/casc/main.html

Thank you very much Zezula for the efforts!

So just use CascView to extract Appearance and Textures directories. Then start the exporter and choose the directory where you just extracted the files. Then it will enum all models and you can export them to .fbx.

Zezula also created a library for reading casc archives, but for now I do not have time to integrate it. May be later.

You can download the updated exporter form here.