A fan brought up a point I’ve long wondered about; why will players want/need to 
co-op in D3? All through development, the designers have spoken of “doing no harm to co-op,” and features like individual item drops and the removal of non-consensual PvP have fixed some of the main problems (as most players saw them) that plagued co-op in D2.
On the other hand, D3 has removed many of D2’s multiplayer incentives, such as huge shared bonuses from numerous Auras, Warcries, and Curses, and the hugely increased drop rates and experience gain in MP games is also gone. Furthermore, the shared stash/gold/Artisans on each account makes solo twinking so easy that you’ll never need a friend to hold a game or item for you, and the Auction House enables trading without ever talking face-to-face.
A fan listed some of these issues in a B.net forum thread, and got a brief reply from Bashiok:
Faster killing speed means more drops, more drops means more power or money. Since the goal of the game essentially boils down to either power or wealth, or both, the advantage (in our opinion) is pretty clear and doesn’t need any additional incentive.
Very curious to hear continued thoughts, though.
We can’t extrapolate entirely from the Diablo 3 Beta, but it’s easy to note that no one ever actually “needs” to play with anyone else in the beta, and thus most people play solo games. A party can up the fun, but in the beta it mostly means everyone running in different directions, trying to find the next level ASAP. Obviously part of that equation is the very easy early game difficulty, but it will be interesting to see if and how players party up to work through Normal and Nightmare once the full game releases. Maybe most of us will just rush through solo, and not start to party until Hell and/or Inferno, where the difficulty increases make the buddy system more necessary?
Benefit of playing coop is that you play with friends. If they add too much bonuses to coop ppl will feel forced to play with someone and hate it. There will be plenty of friends coop games, but almost none random coop. Not without its main use in d2 – trade, pk, griefing.
But i miss one of coop bonuses. Coop crafting. I usually craft for my friends, but its often tiresome to write them down what i could craft them. In D3 it will be even worse as final item will be heavily randomized so i have to show them everything till its something they want. Give me ability to allow my coop players to use my blacksmith and thats all coop benefit i want.
Why is it a bad thing that I am not forced into doing something I may or may not want to do? Co-op in D2 was forced upon players, better drop rates, more exp, more “phat l00t”, all forced players who were even remotely serious about the games, i.e., “hardcores” to play with other people for maximum success. Now, I am no gamne designer but forcing people into playing the game in a way that they may not necesserily want to play is not a good thing. If the human race wasn´t seemingly composed of idiots, jerks, elitists, spammers, etc. I would hold some interest in playing with other people, but after years of playing MMOs, my faith in humanity is at all time low, so I´ll stick with my online single player mode.
I want the same bonuses available as single player. I hated playing D2 with anyone I was always doing stuff solo except for trading and I do not want to be forced to co op.
Also, I love the fact that typical response to “I like playing alone” is something along the lines of sad, fat, lonely, anti-social nerd without any friends, and people talking about playing with friends and being social are the best. And, yet, now that we don´t have any other bonuses except that whole, “power of friendship”, nobody wants to play co-op. Apperantly, just socialising and playing with people aren´t reason enough for co-op.
Yes it is and I bet a lot of people are like me. To me the social aspect of playing with my friends will outweigh the bonuses from coop. But as pointed out above as well, Im sure there will be a lot of single player when no friends are online, due to the nature of most ppl in most online gaming communities these days. (Try playing a HoN game without wanting to “reach out of their screens and punch ’em in the face”).
Playing in co-op is annoying as hell.
You have to wait for them or they have to wait for you when you do something else that killing monsters.
When you go left, they go right.
No time to see the environment, to read lore or anything else.
Rush! Rush! Rush!
In D2, they also took your loot or killed you. Fortunately, they removed this.
All the way solo!
That’s why you play through the game in solo mode a few times first, then do co-op when you don’t care about skipping story bits…
Each player that joins a game increases party damage output by roughly 100%, but monster health won’t increase by that much. Ergo extra players lead to faster kills, faster kills means more drops over time, and more drops over time seems like a strong enough advantage to me.
According to beta testers, each player ups monster health by 75%, additive. So two players, 175%, three players, 250%, and four players 325%. But, as you say, each additional player should be about 100% effective, so 400% DPS versus 325% monsters means you should be flattening monsters pretty quickly.
Mmm and is it possible to do the following thing: I go coop with my friend(friends) one (all) of them go to different Acts and each of us is encountering 175 (250, 325)% of monster HP. That would be pretty chalanging!
I can see both sides of this argument. It totally sucks to play coop with a stranger who will run ahead of everyone and kill everything, or constantly waiting for someone else to play catch up.
However, to say that the build-in incentive of killing more and faster in co-op is a false logic in the case of getting loot. Eventhough you are killing monsters faster in a group, you will also have to split up the loot as well. And the loot does not drop increasingly more in the same proportion as the party size.
I would like to see end game scenarios like D2 in terms of the keys, uber bosses that require pretty much a party to kill.
You have it backwards.
There is no splitting of loot, it is in fact lootx4 in a game with 4 people as each player gets their own drops (all 4 players can get a drop from 1 mob). There is, however, no increase in the quality of loot by having a full game as was the case in D2.
There’s also no loot drop radius. In other words, if a friend kills a mob at one end of the dungeon and you kill another at the opposite end, you both can collect whatever dropped from each other’s kills even though you did 0 damage to the mob your friend killed. There are a few exceptions like Jondar where people do have to be in range since he is not killed by players but the Templar companion (if you are quick enough you can actually land the killing blow before the Templar pops him though).
We always liked playing D2 as a “race” game. That is, we start at level 1 with no gear, and see who is the first one to kill Baal. For a short race game, it was the first to kill Andy. Unfortunately, that meant we had to be in the same room so we could watch each other’s screens.
A dream feature for us would be to have an “observer mode”. It could either be split-screen action, or one window where we play and a second window in full observer mode.
Other games use split screen action like mario kart.
Multiplayer, online solo split-screen.