This is also applicable to the new PvP game from jack's blog

As previously mentioned, Diablo IV is now an open-world action-RPG. What can be gained is more freedom to D2R Ladder Items explore and more opportunities to engage in exciting new activities. Along with the main quests you can also find world events that are happening across the globe making it possible to team with other players to fight large targets, or take on dangerous dungeons.

The most notable features that have been revealed are PvP combat, mounted vehicles to allow more efficient traversal, and the ability to customize your character's build. Particularly, Rune Words (a feature that comes from Diablo 2) are the way to tune your character and further tweak the way they function. Attaching Rune Words grants different effects and stat boosts.

All classes also have skills ranks and talent trees that you can progress through as you gain experience. Skills and talent trees will be vast for each class, and Blizzard said that players will just have around 40% of their skills unlocked by the time they're in the endgame. Also the final game will introduce the meta-leveling system, which is similar to the Paragon levels in Diablo, though not much has been revealed about how this will function at the moment.

The Rogue class is making a big return in Diablo IV. The game hasn't been playable since the very first game.Diablo 4 is an all-day-online experience with a perpetual world shared with other players, even for those who would prefer to experience things as an independent experience. But multiplayer is a big factor in the Diablo experience. Enemies will increase to the level of the party and they will have separate instances with different difficulty levels.

This is also applicable to the new PvP game with the Fields of Hatred. In these areas, players can battle against more challenging monsters and escape with your haul so that you can keep it. In similar fashion to The Dark Zones of The Division incorporates PvP with PvE and  Buy D2R Ladder Items according Director Luis Barriga, it offers for a more tense contrast from the more expansive game.