Melbourne look listless once again as South Sydney consigns them to their fourth successive loss, with the Rabbitohs joining the Storm just outside the top four.
At the top of the ladder, Penrith held off a major challenge from the third-placed Sharks.
Earlier, the Raiders bounced back from conceding two tries in the first eight minutes to beat the Warriors 26-14.
Check out how Saturday's NRL action unfolded below.
Rabbitohs power past struggling Storm
Melbourne is out of the top four, joined by South Sydney on 24 competition points after the Rabbitohs won 24-12 at the Olympic stadium.
With Penrith 10 points clear in first place and the Cowboys, Sharks and Broncos all on 26 points, the Storm, Rabbitohs and Eels are fifth, sixth and seventh respectively after Saturday night, with four teams on 20 points, battling for eighth spot.
Coach Craig Bellamy was at a loss to explain why his players could not stick their tackles or catch the ball, and was not expecting some sort of late-season ambush heading into the finals.
While Souths and Storm are even numerically, their fortunes are going in completely opposite directions as Saturday's game showed.
Melbourne looked out of sorts in attack and fragile in defence as they have during this losing streak, which has now lasted more than a month, with halfback Jahrome Hughes telling Fox Sports the team is "just not up to scratch".
Keon Koloamatangi crossed before the Storm had even touched the ball, and Alex Johnston went over in the 28th minute to give the Rabbits a 10-0 lead.
Only a 65-metre effort from Marion Seve, against the run of play, in the shadows of half-time kept the Storm within reach.
Johnston touched down again after the break for his 15th try from the past nine games, and he was joined on the scoresheet by Lachlan Ilias and Jaxson Paulo.
Winger Dean Ieremia got one back for Melbourne laste in the piece, but the comeback effort never got started as the Storm continued to drop the ball and give away penalties and field position with basic errors.
Penrith Panthers vs Cronulla Sharks
With all of their State of Origin stars back in the fold, the Panthers notched an impressive 20-10 victory over third-placed Cronulla.
The overwhelming premiership favourites looked more like themselves than they did in last week's tight 18-16 win over the battling Tigers, while the Sharks did little to damage their standing in the league as finals approach.
After resting all of their representative players for the clash with Wests after NSW's loss in the Origin decider, Nathan Cleary, Isaah Yeo, Jarome Luai, Brian To'o, Api Koroisau, Stephen Crichton and Liam Martin returned to Penrith Stadium for the showdown with Cronulla.
But it was a slick Cronulla outfit that struck first. And second.
Winger Connor Tracey and five-eighth Matt Moylan crossed in the opening exchanges as the Sharks enjoyed the soaking wet conditions.
But the experienced Panthers did not panic and eventually found their rhythm in attack, sending centre Izack Tago over in the 34th minute and potting a penalty goal on the stroke of half-time to only trail 10-8 at the break.
And they took the lead immediately after coming back out, as Dylan Edwards slid over on the end of a 60-metre attacking raid to end their first set of the half.
The game remained an arm-wrestle in the pouring rain, with Ronald Mulitalo at one stage threatening to strike back with a match-turning intercept, but Luai crossed in the dying minutes to seal the win.
Raiders flip the script on 'Faders' tag against Warriors
After earning a reputation for letting leads slip earlier this season, the Raiders have turned that on its head with a comeback win over the Warriors in Canberra.
The New Zealanders shot out of the gates with tries to Jack Murchie and Daejarn Asi in the opening eight minutes and backed it up with staunch defence and a penalty goal to take a 14-0 lead into half-time.
But the Raiders scored 26 unanswered points to run over the top of the visitors and become the fourth team on 20 competition points in a race for eighth spot.
On the back of an impressive Jack Wighton performance, Albert Hopoate kickstarted the comeback two minutes into the second half when he crossed, but the Raiders had to wait until the hour mark to touch down again, doing so through Sebastian Kris.
That sparked a rush of points for the Territorians, with Corey Harawira-Naera scoring a double as the Raiders put on 18 points in eight minutes.
Coach Ricky Stuart celebrated so vigorously during the blitz that he was left limping after the game.
Harawira-Naera was a small bobble short of scoring a hat-trick, but halfback Jamal Fogarty added two late penalty goals to put the result beyond doubt.
