With the new expansion Reaper of Souls there many interesting changes, which we know so far.
•Less items will drop in comparison to D3 Vanilla.
•Vanilla farming run would give 256 normal, 399 magic, 275 rares and 1 legendary item, in Reaper of Souls the same run would give 73 normal, 266 magic, 83 rare and 6 legendary items!
•White items will be useful as a new crafting reagent.
•Smart Drop is a system which gives each item a chance that its affix rolls will be focused on the class currently being played.
•From some of the items seen (3k DPS and 300+ mainstat weapons), the new Level 70 items will have more potential and (eventually) overpower all current Level 63 Affix Items.
•All Legendaries can roll at all levels (with power/affixes and level requirement that match that level).
•Legendary will be build-changers, by drastically changing particular skills.
•The Paragon system has had a huge overhaul. It is no longer per-character, but account wide
•Instead of the current bonuses your account gains 1 Paragon Point per level to spend on different stats
•No longer has a cap
•Stats are separated into Core (Str, Dex, Int, Vit), Attack (Crit Chance, Crit Damage, Attack Speed, Cooldown Reduction), Defense (Health %, Resist All, Armor, Dodge %, Block Chance %) and Utility (Run Speed, Magic Find, Gold Pickup Radius)
•Paragon Points can be respecced
•Each Paragon Level adds one paragon point to all your characters. You can distribute them differently for each character
•Retroactively Paragon Points will be determined by your overall experience gained so far, not the sum of your Paragon level number for your characters
•Paragon levels are separate for Normal and Hardcore modes
•Dying in Hardcore does not take away from your earned Paragon Points