I've only played DS and Diablo 2 multiplayer with some friends. I would probably get bored quickly in single player. Though DS has some nice advancements on Diablo. The ability to allow your character to do some things on his own is nice. I had mine guarding one of the other members, and he would attack whatever he could. I used that a few times to get up and grab a drink, and not stall the party.

The multiplayer campaign seemed to vary the monsters quite a bit. And the ability to level a character however you want is nice. And not having to click a million times (I classify Diablo 2 as an Action game due to that) was also a good change.