With hooker Wayde Egan pulling all the strings at Accor Stadium, Andrew Webster's side joined Penrith and the Sydney Roosters on 38 points.
The Warriors (+295) needed to beat Souths by 19 points to move past the first-placed Panthers (+294) on points differential.
And they did just that with rookie five-eighth Luke Hanson's 80th-minute field goal getting the job done after the Bunnies nearly pulled off a spectacular second-half comeback.
The Roosters (+163) have a game in hand and will play Wests Tigers on Sunday.
Even if this was a bit of a Jekyll and Hyde performance from the Warriors, Webster's side, who lost winger Dallin Watene-Zelezniak to a shoulder injury, showed signs that could be a genuine contender to be back at Saturday's venue come grand final day.
Deploying fourth-choice No. 6 Hanson with Chanel Harris-Tavita, the Warriors hit the Rabbitohs with a sledgehammer in the first 20 minutes with tries to James Fisher-Harris, Leka Halasima and Mitch Barnett.
Jack Wighton and Alex Johnston hit back for the Bunnies before Harris-Tavita backed up a blistering Eddie Ieremia-Toeava break to put the Warriors back in the box seat.
Fullback Taine Tuaupiki converted Harris-Tavita's try and then added a penalty to give the Warriors a 26-8 halftime lead.
Watene-Zelezniak crashed in on the right straight after the break, before trudging off.
Souths' problems were only amplified by their struggles from the tee, with Jayden Sullivan missing both of his first-half efforts.
But the playmaker made no mistake with his next three as Johnston, Cody Walker and Tallis Duncan all crossed in a 12-minute onslaught.
The Bunnies were just six points behind with 20 minutes left, but tries for Jacob Laban and Alofiana Khan-Pereira moved the Warriors out of sight.
Leading by 18 heading into the final minute, Hanson showed a calmness by receiving an inside ball from Harris-Tavita and slotting a one pointer from 30m out.
The Warriors host Newcastle and Manly over the final two rounds, while Penrith face Canterbury and Wests Tigers.
The Roosters square off with the Dolphins and Souths to round of their regular season.
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