Viscount bug?
Same thing is happening to me also.
Possibly related. Did you kill him on a character that has done the instance with Tassi? The first instance where you get the golem and Tassi mails you the finishers.
Same problem, using same character always.
Saleen – Maguuma
Yes, this was after the fact. I killed him 6 times now, still nothing.
Hiya, I was able to get the achievement but this time I fought in melee range. I am not sure if that is the trick.
Saleen – Maguuma