The Abt Audi driver, who recently announced that he will switch to BMW for an undisclosed racing programme next year as well as joining McLaren in Formula E, had two incident-blighted races at the Eifel circuit that saw him lose crucial ground in the title race.
He scored only two points for finishing ninth in race one after multiple contacts, including being spun by Laurens Vanthoor, and retired from race two after being turfed into the gravel by David Schumacher at the final corner.
From 10 points adrift of pre-event points leader Mirko Bortolotti after a brace of third places at the Norisring, he is now 29 points adrift of race one winner Sheldon van der Linde, and railed against the driving standards in the championship when speaking to TV crews on Sunday.
Describing his tangle with Schumacher, Rast said: "The first time he hit me in the chicane, then I had a bad exit, and then again he tried to pass me and hit me again in the rear, spun me in the gravel. Unacceptable.
"Driving standards this year in DTM are unacceptable, they drive like little kids. They have no experience and it’s really no fun to drive anymore.
"I think some of them have to go back to the support series, get some experience and then come back to DTM. But like that it’s no fun to race anymore."
Asked if he wanted to see a consequence for the incidents, Rast added: "I hope so. Not only for him, for many other drivers.
"You cannot race anymore, it’s just a gamble. Some of them leave a space, some others not.
"You cannot go side-by-side through the corner anymore, they push you on the grass, they hit you up the back, they spin you around. It’s just a gamble.
"For sure we have to do something against that."
Speaking to Autosport after race one, when he was embroiled in three-wide contact on two occasions and "got hit from all sides basically", Rast said it had been "for sure one of the ones where I had the most contact".
"Driving standards, as at the Norisring, are quite bad," he said.
"We saw that already at the Norisring, people drive like bumper cars almost.
"It’s a bit of a shame because we have the pace, we have a good car, we try to stay out of trouble but sometimes you’re on the unlucky side all the time and you’re taken out of the race."
Rast defended himself after furious comments from Team Rosberg Audi driver Nico Muller, who told TV crews that the race-ending puncture he'd picked up after a touch with Rast exiting Turn 1 was "completely unnecessary".
"I was next to him after Turn 1 and he kept moving to the right when I was on his right-hand side and we had slight contact, but it was for sure not on purpose," Rast told Autosport.
"We are Audi team-mates, we’re still Audi team-mates and for sure I’m not driving on purpose on his tyre.
"There nothing I could do when someone is moving to the right and I’m on the right, at one point I still have to survive."
He also questioned why Vanthoor was given a five-second in-race penalty for their collision, when the Belgian had already retired.
Asked if he was planning to speak with race director Scot Elkins about driving standards, he told Autosport: "Normally there should be a penalty for the next race in these kinds of situations."
