4E and Diablo 2 have a lot in common, at least more than 3E had.
Ask yourself, what does 4E bring to the table:
- A balanced, but highly abstract combat system
- A highly abstract HP system
- Characters defined by class with not much way to go outside it
- Magic items which, among other things, increase the class powers
- A economy/world which would not work and only exists for PCs to trade magic weapons
- A focus on evil monsters to be killed. "When you don't fight it you don't need its stats"
- The system doesn't support out of combat abilities and roleplay very much. It only happens in your head
And now Diablo 2
- A balanced, but highly abstract combat system
- A highly abstract HP system
- Characters defined by class with no way to go outside it (Titan Quest would be a better fit here)
- Magic items which, among other things, increase the class powers
- No NPC interaction except quests and buying/selling.
- A "If it moves, kill it" environment
- The only out of combat abilities are gambling for magical items and crafting with that cube thing. And roleplaying is not in the game and can only happen in the mind of the player (or when talking to other players who want to role play over chat/teamspeak)
That are quite a few similarities.