Blizzard has said that its the improvement of Diablo 3's co-op gameplay will be the focus of its next update.
In particular, the firm talks of improving co-op farming efficiency, and "a number of other hurdles" including a new 'Identify All' inventory feature.
Here's the full statement from a Blizzard rep:
"We are looking to improve co-op farming efficiency in 1.0.8. Co-op play in general is a big focus of the 1.0.8 patch and efficiency is definitely one component of that. Co-op is already more efficient for some players, but this is the exception rather than the norm. The degree of co-op efficiency depends heavily on the co-ordination of the party, skill builds, and the relative gear level of the teammates. Since launch we've made some modest changes to encourage co-op play but there's still room to go farther. At the same time, we don't want to go so far as to make multiplayer feel "mandatory" for those who prefer to play solo, but we still want to err on the side of being co-op favorable.
"There's also a number of hurdles to co-op play beyond raw efficiency, so we'll be looking to alleviate/solve some of those hurdles too. The Identify All feature in 1.0.8 is an example of this. Sometimes the trip back to town to sort through a bag of gear is enough of a hurdle to make somebody feel playing co-op isn't worth it. Nobody wants to be in the dungeon fighting monsters while your teammate is off in town identifying a full inventory.
Diablo III has sold more than 12 million copies worldwide as of December 31, 2012, claimed Activision, before finally officially confirming the game for launch on PS3 and PS4.