ISP: Bell Canada

Type of Internet Connection: DSL

Internet Connection Speed: 16Mbps

Date & Time: Between October 30 2014, 6:00PM and 6:30PM eastern

Frequency: Always

Character Name: King Canadane

Race: Miqo'te F

World: Hyperion

Class/Level: Warrior/50

Area and Coordinates: The Striking Tree

Party or Solo: Party, 8

NPC Name: None

Monster Name: Ramuh

In-Game Time: Multiple times

Steps:
Advance through the fight until Ramuh summons the arbiter adds. At this point, killing the final add triggers Ramuh's signature attack, however it wipes the party as if the arbiters were not killed in time.
At first we simply thought we weren't quick enough. We managed to do this a second time with 25% echo buff, ensuring we were well within the time limit imposed by the adds. There wasn't any question about being close to failing or not. However the result was the same. Ramuh's signature attack did damage equal to that when you fail to kill the adds.

Last I've been through the fight without issue was before the 2.4 patch.