Short answer:
Blizzard has not announced any plan to introduce an offline mode. Given the game’s MMO-lite design, a full offline mode is unlikely unless a major rework happens (similar to Diablo III on consoles, which later got offline mode — but D4 has a different architecture). diablo iv offline mode install
Once the files are located, you only need a tiny amount of data: Short answer: Blizzard has not announced any plan
You cannot install Diablo IV without an internet connection, and you cannot play it indefinitely offline. The best you can do is install once, then reconnect every few weeks for a quick authentication. The best you can do is install once,
While some community projects attempt to create private server emulators (similar to those for other online-only games), these are unofficial, often unstable, and can lead to permanent account bans.