The original Diablo 2 could be played offline or with friends without using Battle.net, so those can be worked around. I'm guessing with the "cross progression

The original Diablo 2 could be played offline or with friends without using Battle.net, so those can be worked around. I'm guessing with the "cross progression" system (whatever that means) that games will have to be on Blizzard's servers at all times to allow syncing and avoid cheating, hacks, and piracy.