I was able to download D2:DC from the Larian Vault and install it without any errors.
How soon do you get an error about missing source files on the server? You could just try again; enough time may have past by now for any updates to finish or corrupt files get replaced.
Alternately, I created some
QuickPar recovery files which could be used to fix minor corruption:
par2 file (59 KB),
3 recover blocks (8MB). After installing the program, download the par2 file and extract it into the 'Div2DC_EN' folder where you downloaded D2:DC. If there was only minor corruption in each of the 3 files that gave errors, you may be able to download the recovery blocks to repair the files. More likely there will be more than minor corruption. Let me know how many recovery blocks are needed, and if practical I can create enough recovery files.