There is one optional quest, though I don't remember which one, in Ul'Dah, where you have to investigate a death and when you go into the crypt the priests there tell you how they have eto treat the body to keep it from dissolving. That kind of treatment would surely not be done on a battlefield or in the wilderness, so people still canonically dissolve into aether, as far as I'm aware.
Between that and us getting the corpses from the attack on the Waking Sands to a graveyard, I assumed it'd take maybe a couple of hours in some cases for the body to dissolve and the burial being done for ritual purposes, rather than the pragmatic reasons that make it so important to bury, burn or treat dead bodies in our world to avoid the spread of disease (naturally in addition to the social aspects). And accordingly there would be this window in which someone could turn those not-yet-dissolved corpses into undead.