Mercedes factory driver Auer had looked set to score a first victory of a 2023 season that he began by injuring his back at Daytona, the Austrian taking the lead from polesitter Ricardo Feller on lap seven.
But Grasser driver Paul showed rapid speed after putting on a new set of wet tyres late in the race, snatching the top spot from his Winward rival with 15 minutes to go.
The result made Paul the eighth different driver to win a race in as many races this season, and secured a clean sweep of victories for Lamborghini at the Nurburgring following SSR driver Mirko Bortolotti’s own maiden success on Saturday.
At the start of the race, Abt Audi’s Feller led the field from pole position, while reigning Sheldon van der Linde dropped down the order to promote Winward duo David Schumacher and Auer to second and third positions.
Feller established a comfortable lead up front but having selected tyre pressures that proved too high, he started to fall into the clutches of the chasing pack as rain began to hit the track. Auer soon charged past the Swiss having already overtaken his team-mate Schumacher for second.
Feller waited until the pit window opened after 20 minutes of racing to take on wets, elevating those who had started on the grooved Pirelli tyres.
One of the biggest gainers was Paul, drafted in to replace Mick Wishofer on a one-off basis at Grasser. Starting 13th, the ADAC GT Masters podium finisher quickly made his way up the field before passing the similarly wet-shod cars of Laurin Heinrich (Bernhard Porsche) and Schumacher to snatch second position behind Auer.
Auer, Paul and Heinrich elected to go long in the first stint and their strategy paid dividends when a FCY was deployed to recover the stranded Lamborghini of Alessio Deledda, who spun at Turn 1 after being caught out by the Emil Frey Ferrari of Jack Aitken that had just exited the pits.
This brought the trio firmly ahead of their rivals, setting up a three-way fight for victory.
Auer initially appeared to have done enough, but Paul began to rapidly close in despite the Mercedes driver’s 10kg success ballast not proving much of a handicap in the wet conditions.
After a duel that lasted for several laps, Paul moved ahead into the hairpin and with a clean track ahead managed to pull away and secure his and the Grasser team's first DTM victory in only his fifth series start.
Heinrich also managed to pass Auer to take second, scoring his first DTM podium in the process.
Auer held onto third place ahead of the fellow Mercedes of Maro Engel, while championship leader Thomas Preining finished fifth in the Manthey EMA Porsche.
Feller eventually came home in sixth, while Luca Engstler finished seventh in his family-run Audi after completing his pitstop just before the Deledda-induced FCY.
Emil Frey’s Thierry Vermeulen, another driver to stop late on, scored his best DTM result in eighth, while Schumacher and SSR Performance’s Franck Perera rounded out the top 10.
It was a tough race for BMW’s van der Linde, with the decision to start on slick tyres backfiring and leaving him 17th at the finish, one place behind the fellow M4 of Project 1 driver Marco Wittmann.
