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.
Lots of good comments here! Just a few quick points
1. As a point of clarification, "dropping less loot on the ground" is not slated for 1.0.8. It's part of our general philosophy for beyond the 1.0.8 timeframe.
2. I really like the suggestions that don't make multiplayer feel mandatory. Suggestions along the lines of "I don't want to feel penalized for playing with my friends" or "provide a small bonus to overcome the logistical overhead" are in the scope of what we're thinking.
3. We totally see the appeal of having more than 4 players in a game, but it has its downsides, and the big one is that the screen becomes so crowded you can't tell what's going on. It's important that a player can discern important information from the game world and make tactical decisions based on this information. We know some of you may disagree and you'll always want 8 players, and I can respect that. This is something we've debated heavily though, and feel strongly about.
4. We've discussed the "leecher" problem. Nothing to share yet but it's definitely rough when it happens.
Thanks for all the great discussion thus far!