If you can't figure out any other option, I have a solution that does not require file modification. Download a copy of VMPlayer and a copy of the Ubuntu 13.10.iso or a linux distro. Copy over your existing diablo file to the virtual and play it through WINE. I say to use an ubuntu or linux distro due to the minimal resource requirements. Do not use VirtualBox or Oracle Virtual as their baseline resource requirements will severely hinder multiple virtuals running and DB on top of that.
Edit: There is a massive perk to using virtuals. If for some reason Blizzard decides to collect data on what IP you're coming from via the battle.net/game instance or if they take the time to tear down session packets or headers, the virtuals will render as distinct boxes. Each, though NAT'd through your public facing IP, will utilize distinct sockets (IP and Port combinations) with the host server. I could go into more detail if necessary but wanted to toss this little perk out now.