ISP:
Atlantic Broadband

Type of Internet Connection:
Cable

Internet Connection Speed:
1.5 mbps

Date & Time:
3:30-4pm Eastern

Frequency:
Always

Character Name:
Ashkendor Zahirr

Race:
Miqo'te M (Lalafell M also received the same drop)

World:
Sargatanas

Class/Level:
level 50 Paladin

Area and Coordinates:
The Whorleater

Party or Solo:
Party of 8

NPC Name:
None

Monster Name:
Leviathan

In-Game Time:
Not sure, didn't notice till later what had happened

Steps:
1) Clear Leviathan EX
2) Leviathan's Barb drops instead of Barb of the Whorl

It happened 2 times during 4 runs, proof here:

http://puu.sh/cwFNz/442ef1d6c7.png
http://puu.sh/cwFNz/442ef1d6c7.png