Horadric? Not sure if you're familiar if that name, but that's the language and people who Tyrael initiated to capture the 3 brothers before D2. They show up again in D3, but a new generation.
Part of D3's development is that they got rid of all pentagrams and what not so it didn't connect to real life stuff. This may have included the languages used....
I would guess it to be Khanduran or "common western kingdoms" but some of the Diablo books might get more specific.
The wiki has some info about languages also https://www.diablowiki.net/Sanctuary#/editor/4