The exciting story of Diablo 3 development:
1. In Diablo 2, players would only pump stats up to a certain cutoff point, determined by gear requirements or block/dodge caps, and put the rest of their points into Vitality, since none of the other stats offered a major enough benefit.
The Average Player: Well, they should rebalance stat importance for Diablo 3, so that they make a noticable difference at higher levels, perhaps even award more points later on. Ideally, the player should have to choose between damage and survivability by making stat allocation choices.
Blizzard: Just remove stat allocation altogether.
Syril: Excellent decision, Blizzard! You guys are so smart!
2. In Diablo 2, even though the skill trees seemingly allowed for a lot of different builds, players focused on MP would still use one of the few optimal ones.
The Average Player: Well, why is that bad? Everyone gets to do what they want to do, a casual SP player can win with random crap, while the hardcore MPer can have fun figuring out what the optimal build is. And with a good skill-tree, we will undoubtedly see builds the designers hadn't anticipated. It would be best if they took the ideas developed while patching D2 (like synergies) and improved upon them further.
Blizzard: Remove skill trees, too complicated for our new target audience.
Syril: Totally agreed, Blizzard. I know you will design the new system so that it allows for even more choices than the one in D2.
3. Always online, even for single player.
The Average Player: Why do I need to suffer the typical online annoyances - like lag and disconnects - if I only want to play single player?
Blizzard: This way you don't need to distinguish between SP and MP characters. And believe us, our new Battle.Net service is so good, you'll never want to be offline!
Syril: (Difficult to talk with a cock in mouth)
Don't worry Syril, my friend, I only used you as a stand-in for Blizzard fans so my work could resonate with the Codex audience better.