Never thought I'd ever get that achievement. I might have done it once in the past but I'm not sure.
My board doesn't look that strong but it was a very quick game (12 turns I think) and the closest rounds were the first 2. Last 2 rounds I even had 98+ win percentage, I never really was close to not winning a round after the first 3-4 turns.
My BG rating is about 8700 and was around 9k before the reset.
Not even that strong of a board for Murloc, only one poison with no shields - I've had much stronger boards and only managed 2nd/3rd with them. Maybe elementals were out? they can out pace strong murlocs as they get monstrous earlier - esp if you grab an early Domi from a triple