Fifth, in terms of online and extended functions, continue Diablo 3's online functions, but hold off on Challenge Rift and Ranked.
Diablo 3's Challenge Rift system was an excellent design, except for the fact it was a double edged sword.
When the players want to just kill a large number of enemies, they would obviously default to levels in the story with high spawn rates. Blizzard decided to release Challenge Rift to allow players to do so with ease without the need to go through the story again and again.
This was a good news to the players who liked the feeling of hacking and slashing as they saved them time. However, this damaged the lifespan of the game to a certain extent, making something that the game is incredibly repetitive.
Chen Mo planned to release Challenge Rift in an update after the main release. By that time, the players that remained are loyal fans who are sick of the story who would enjoy something like Challenge Rift.