I've been a long time Diablo 2 fan but I was rather disappointed at Diablo 3's failings... well I LOVE Reaper of Souls! I'll explain...
Most of D3's failings revolve around the auction house. Well, they took that out, and thank you lord now you actually look for, craft, and trade items! That was the core purpose of Diabo 2, and it's back.
The game no longer ties monster levels to difficulty level. You are able to access Normal, Hard, and Expert right out of the gate. These difficulties can be accessed at any level and come with enhanced XP/Loot for trying harder
When you beat the campaign Master difficulty unlocks and that's pretty much the standard for a decently geared and skilled player who hasn't maxed out yet.
The EXP Bonus is kept relevant 100% of the time by the Paragon System, with which you will continue to gain levels after reaching the maximum level. These Paragon levels allow you to assign points to your extra abilities such as "Cool-down Reduction", "Resource Cost Reduction", "Enhanced HP", and more. Paragon Levels are shared across all characters on your account with the exception of the Softcore/Hardcore divide.
Hardcore works similarly with your Shared Stash and Gold; they are still account-wide but will not cross the Softcore/Hardcore barrier.
Now for the best part of Reaper of Souls: ADVENTURE MODE.
After you finish the main campaign, Adventure Mode Unlocks.
Blood Shards are used to purchase a random quality item - type of your choice from Geed's daughter, yup, it's a new version of Diablo 2's gambling system.
When you collect enough Rift Key Fragments, you can open a Nephalem Rift. (Spelled Nephilim in the Bible.)
To understand the Nephalem you have to understand Diablo's story. In the beginning there were only Angels and Demons, they warred. Eventually renegade Angels and Demons created a new world so they could stop fighting, these renegades named that world Sanctuary. The spawn of Angels and Demons mating were the Nephalem AKA Humans. But not ordinary Humans, ultra powerful humans. The Angels and Demons began to fear the power of the Nephalem and they altered the Worldstone so successive generations would loose their powers and have to do things like eat, drink, and sleep and have short lives.
Not all Nephalem shared that fate, to sum it up, all the Diablo 1, 2, and 3 heroes were Nephalem descendants; that's how they can level up and destroy demons that would overwhelm an army of normal humans.
So, you click on the Nephalem Obelisk and a rift opens, the rift is a 100% randomly generated dungeon (think Torchlight) where you can be in the High Heavens go down some stairs and be in the Tristram Crypts, then go through a door and end up in the Westmarch streets. All the monsters randomized in a scary cluster fashion, think Diablo 2's final act post-patch when guest monsters from other acts started entering it.
In the rifts you have a goal, to kill enough of the monsters inside of a rift to summon the Rift Guardian, one of several named/and themed bosses with a uniquely deadly assortment of powers. Each Rift Guardian has a much, MUCH higher chance at dropping a legendary quality item than other enemies.
Fun Facts about the new and improved Diablo 3
- After you finish Act 5, ALL characters on your account can play Adventure Mode, if you don't enjoy running the Campaign Mode again, you can level your other characters via Adventure Mode. Keep in mind this does respect the Softcore/Hardcore barrier though, so you'll still have to do the campaign if you want to play adventure mode on the other side.
- You can get Blood Shards on your Max Level character, and then spend them on a lower level character to get level appropriate gear via gambling.
- They added a Clan system, so keeping track of what your friends are up to is more fun than ever. You can make clan posts and whenever a clanmate loots a legendary item you'll see it. Clans have their own chat channel.
- They added a community system so people who like the same stuff or are intrested in the same stuff, but not to the extent you want a bunch of randoms in your clan, you can just join a community; unlike clans you can be in more than one! Communities each have their own chat channel.
- The entire game is fun, Softcore or Hardcore! But hardcore players are just plain cooler.