Is there another downloading method beside Battle.net Client?

Hey there,

Installing through the Battle.net app is the only supported method.

If you have access to a different computer with a faster internet connection you could possibly download Diablo II Resurrected through the Battle.net app there then find a way to transfer the game data over to your PC (a large USB drive for example). You would want to transfer the entire Data folder which is where the bulk of the install is (around 28GB). On your PC you could start the game install so it creates all the other files, then pause the install and copy in the Data folder. When resuming the install the Battle.net app would check the data files that were copied in. Should be playable at that point.