Can't Loot Nightbane in Return to Karazhan
Common ProblemsI can't loot Nightbane because his corpse is in the air.
The loot from Nightbane in Return to Karazhan is delivered by The Postmaster even if you aren't able to reach the corpse to loot it. You will need to wait a few more hours for the items, but they will be delivered to you in mail.
If there was no mail, Nightbane did not drop any loot for your character. You can read more about the calculations behind the Nightbane loot system here.