Well we want to play the story-mode in co-op. But they are only single-player in the beginning, so will there be some missions playable in co-op? Or do we have to play those on our own?
Developer: Naaaa, pay me to play the game my way.
Its the number one feature that would make this the best ARPG ever. They have made up reasons about being too easy, or cheating or insert random thing that's not actually a real problem but sounds good to players who don't know any better.
Now, technically there is currently a feature you can take advantage of to play the fun missions in co-op.. unfortunately they probably don't want anyone mentioning on here because they don't like people playing the story together and it can bug out your account. (You can look it up elsewhere though). I don't recommend it though.