Diablo is back and entirely different than ever before. With Diablo III and its Reaper of Souls expansion, Blizzard has recreated one of its defining franchises to be both console friendly and appealing to a much broader audience. Don't let that fool you, because Diablo III will still make anyone's fingers bleed from clicking the mouse and loot still rains from the sky like the player is a living Scrooge McDuck.
For instance, there are no Necromancers. Not a single playable one. Instead, players will be able to pick from Wizard, Monk, Demon Hunter, Barbarian, Witch Doctor and with Reaper of Souls the Crusader. Each class has a number of skills which will unlock as the player levels. The player can mix and match thse skills as they please without Skill Points like in Diablo II. However, only so many can be used at any one time, so choose wisely.
Diablo II may have erased the Prime Evil from the world, but if you think that means there isn't more story to be uncovered then well, I mean its named Diablo III. Think about it.