I've reported this bug before, and it is still broken.

Level of Character: 35
Location where bug occurred: Mark Clemen's instance dungeon in McGee's Mine
Quest Name: Lies, Lies, They're All Lies
Description of the bug: If I go in this dungeon with a friend, both of us see the yellow question mark over Mark Clemens head. If one of us talks to him, the 12 round battle starts for both of us, and the other still sees the yellow question mark over Mark Clemens head. Once the 12 round battle is over, the one who started the battle sees that his quest has changed to talk to Marshall Dillon, the other says to talk to Mark Clemens. When the second talks to Mark Clemens, the battle starts all over again. What SHOULD happen is that when one talks to him, it registers for everyone in the dungeon, and it does not.
How Often Does This Bug Seem To Happen?: Every time.
Were you playing Solo?: No
If You Were In A Group of Playing With Others, How Many?: Two total.
Were You The Only One To Experience This Issue?: It happens to everyone who does not talk to Mark Clemens first.
Can You Reproduce The Bug: Absolutely. Happens every time you go in with a group, all of whom have the same quest.

Username: MaxDeGroot
Area: McGee's Mine, Mark Clemen's Instance Dungeon
What Time?: Approximately 9:00PM EDT

Is The problem still occuring?: Yes, unless I want to fight the 12 round battle again.