Locate Corpse  

if the corpse is not yours be sure to have your party member in the zone so that you can target them

1: open your map (M)
2: open the map editing tools (small button at the bottom looks like a compass)
3: target the party member and cast spell to point you toward the corpse
4: click "start line"
5: walk some distance, maybe 10 yards
6: click "end line"
7: move off left or right some distance maybe 100 yards or so
8: repeat steps 3 through 6

you should now have two lines not quite parallel

9: select both lines (hold down shift to select both)
10: with both selected (highlighted) click "join at intersect"

the corpse is located at the intersection of the two lines.