The main reason for the corpses not being able to stay permanently is the potential number of them on screen at one time, and specifically that each corpse is affected by physics, allowing them to be blasted and thrown all over the place by the force of player abilities.
It's one of the trade offs when integrating new technology, you can get really awesome effects, but they do have a cost. In a 2D world, a sprite of a dead creature doesn't really cost any more (system requirement-wise) than a sprite of something that's alive. Probably less. In a 3D world where a creature dies and then needs to have physics calculations thrown onto it so it can bounce and fall and fly around, they cost substantially more.
We remember fondly those situations where you've just completely obliterated a camp of Fallen, and as you're picking up items - marvel in your destruction. That's a feeling and part of the gameplay where if we can realistically keep some of it without sacrificing features or having insane system requirements we'd definitely like to, but no promises.
When questioned as to how skills like Find Item, Corpse Explosion and Summon Skeleton would work in D3, if they were indeed included, he responded:
We haven't announced any abilities outside of those listed on the website, so by discussing what is or isn't in the game I would be essentially making an announcement, which I'm not prepared to do.
Thanks for the tip, Dead9k!
indeed. his skills are very similar to the Witch Doctor skills we know about and as Blizzard said: No class will be similar to another. Necromancers are lore for now. So are corpse using abilities i guess.
Vanishing corpses + floating critical hits numbers = WTF ?!
Remember what Blizzard said? This game is specifically made for online playing, but single player option is available. So they'll obviously focus on multiple player gameplay.
If you can have the option to choose when the corpse disappear, that should only be on singleplayer, but this would not work on multi player (assuming most of you play online instead of single player.). If we assume the corpse could be used for something, maybe corpse explosion, wouldn't really make sense to have the floor randomly blow up if someone turned the corpse vanish on and some turned it off.
As someone have mentioned before, they should make the corpse vanish if the section of the area is demonless. So they basically split up monsters into groups, and split them in different sections of the area. And they wouldn't leave the section they were placed onto. When that specific section is demonless, the corpse vanish. But if their were say 1 or 2 demons left, the corpse don't vanish. This is just in case the demons can ressurect the other dead demons.
This way, they can control the amount of demons on screen each time, and avoid lag. Of course the corpse only vanish if the area is demonless for about 3-4 minutes.
I'd then go on multiplayer casually just to showcase my gear, or mess around. Since Diablo 3 will " hopefully " offer some decent PvP, that's a reason why I'd go online mostly. The PvP brings the community online, so I hope Blizzard realizes that and makes it one of the key focuses instead of wiping it to the side like most companies do with their Hack N Slash game. But it sounds like Blizzard is incorporating the same Online system Titan Quest used in terms of hosting a server, and players being able to join at any time and pick up where they left off in their single player campaign. I also liked to go online for the increased difficulty, since every player that joined, popped up a message saying the difficulty has been adjusted, which added more creatures, hero level creatures, and loot.