Did you friend hit respawn or exit? Cus what you are describing is a result of that. My friends (and me) die plenty, but we wait in the dead or unconscious screen till the char is stripped (by friend or foe), then exit or respawn.
If you kill a hostile and their body aint there, thats a combat log, same thing as above just a different name (i think the combat timer is on its way).

With zombies you are correct, but that is afaik related to them not having any loot and maybe performance?