I would like to see this type of blog for D4, anyone else?
If I have to read lore outside of the game to know “what the Burning Hell/High Heavens going on?”, that’s an instant loss of a star from my rating of the game
For the most part, just playing the games (and actually paying attention to the story) is a good enough way of learning the general lore of the games. External material (like books and such) mostly serve to fill in some gaps, explain in finer details, and/or tie up loose ends.
As for D:Immortal, since the game is set after the events of Diablo 2 LoD, then I would consider knowing the events that had transpired on that game to be a pre-requisite for having a firm understanding of the events to be in D:Immortal.
That said, I’m sure D:Immortal will give a recap of sort through either cutscene, in-game dialogue, quests, etc; so that even new players who never played a Diablo game will have a grasp on the situation.
Long story short, there shouldn’t be a need to read external lore in order to know what’s going on.