Thanks, LyquidBashiok: First, touching on the corpse fade timers as they stand, the tech to have them last longer has been in for a while. Pretty much how it's working is that there's an allowed number of physics "actors" that are allowed to remain at a time. These actors could be corpses, but they can also be pieces of destroyed tables, or railings, etc. anything that relies on physics. These are corpses and destructables generally. As you 'create' physics actors the oldest ones disappear. So as you're fighting there are always a number of actors remaining in the world, and it works out pretty well. Obviously how many of them can remain at one time will come down to final performance tweaking, but right now I believe it's around twenty.
On to blood and fading; the "cost" of decals, which include the blood stains, are fairly high. Cost being the relative strain put on the machine running the game. Decals account for blood, but they also account for quite a few other effects, most of which haven't yet been revealed. In the potential case of a full party creating these decals, blood flowing from creatures, skills that create them, as well as monsters themselves using skills that create them (Wretched vomiting all over the place is a good example), there is the potential to have a large number of decals on screen at any one time. So again, it's going to come down to final performance tweaks as to how many of them will remain on screen and for how long.