Brisbane's finals hopes are in tatters after St George Illawarra hung on to win 30-26 to give last year's grand finalists their sixth consecutive loss.
No team in NRL premiership history has lost that many games in a row and won the title.
The Dragons pack mauled and monstered the Broncos in the first half, with second-rower Jaydn Su'A, dropped from the Queensland side, playing one of his finest games against his former club at Suncorp Stadium.
The visitors scored three of their four first-half tries in the space of nine minutes to lead 22-6 at the break to stun the crowd of 34,224. Three of those tries followed Brisbane errors.
Broncos coach Kevin Walters summed up his side's woes.
"The simple errors … you can't keep doing that," he said.
"We paid the price again tonight. It is not changing, is it?"
Dragons coach Shane Flanagan said he was proud of the way his side dominated early.
"Our first 40 minutes was Dragons-like and the first 10 minutes of the second half was pretty good as well," he said.
"We let them come back for a scramble, but we were good enough to get away with it from what we did in the first half."
Winger Christian Tuipulotu scored his first career hat-trick, with his first-half double showcasing brute strength and willpower.
With 24 minutes remaining, and trailing 28-6, Broncos five-eighth Ezra Mam showcased his physical power and forced his way past fullback Tyrell Sloan to narrow the margin to 16.
In the 63rd minute fullback Tristan Sailor, who had not enjoyed a happy night, found centre Kotoni Staggs with a flick pass and the Brisbane skipper raced 55m to bring the crowd to life.
Dragons No.6 Kyle Flanagan landed a penalty, but Sloan was poor on defence to allow bench hooker Blake Mozer to crash over.
Staggs brushed past Sloan to set up a heart-stopping finish.
Brisbane were woeful for the opening three quarters and have slipped four points out of the top eight. They must now win six of their last seven games to play finals, while the Dragons have moved into eighth position.
"The thing that annoys me is that I know we are a so much better team than what we are doing," Walters said.
"I am just disappointed that is what we throw up and I am disappointed in myself as a coach that is what is being presented consistently. That is it not good enough. That rests on me."
The first 50 minutes was all the Red V, with the pack dominant. Tuipulotu powered over after a slick ball by Mosese Suli in the seventh minute. Staggs was sin-binned and Suli burst through flimsy defence just before the Broncos star was about to come back on the park.
Tuipulotu crashed past four would-be defenders after a classic pass by Flanagan.
A bomb by half Jesse Marschke was spilt by Sailor and Su'A swooped to score and give the Dragons their best first half of the year.
