That time went unbeaten and the second flying lap runs were delayed when R-Motorsport Aston Martin driver Jake Dennis slowed to a halt at the Ramshoek bend and caused a red flag.
Once Dennis’s Aston Martin Vantage was towed back to the garage, the session resumed and in the final five minutes, few drivers appeared capable of dislodging Wittmann.
Rast’s last flyer started promisingly with a first sector that put him in contention for pole but the Audi driver then had a poor second and third sector that left him second on the grid.
Audi stablemate Nico Muller had looked set to challenge for pole until he got briefly sideways on the entry to the Geert Timmer chicane and put two wheels onto the gravel, having his laptime deleted.
That meant Loic Duval helped seal an all-Audi top four with WRT’s Pietro Fittipaldi an impressive fourth for his best qualifying result of his rookie DTM season.
BMW’s Timo Glock had been Audi’s closest challenger during Friday’s free practice sessions and he sealed fifth ahead of Muller.
Sheldon van der Linde had his best lap deleted in the first runs and headed straight out following the red flag to set a time good enough for seventh on an empty track.
Norisring race winner Bruno Spengler was eighth ahead of fellow BMW drivers Philipp Eng and Joel Eriksson.
WRT Audi privateer Jonathan Aberdein was 11th ahead of local driver and practice pacesetter Robin Frijns.
Daniel Juncadella was the leading R-Motorsport driver in 15th, qualifying ahead of Paul di Resta, Ferdinand Habsburg and Dennis, who did not return to the session following his earlier problem.