Neither featured in Dortmund's 2-0 DFL Supercup victory over Bayern Munich on Wednesday and their reintroduction to competitive football proved tricky against determined 3. Liga opposition.
Reus, back in the side after three months out with ankle ligament damage, had a quiet match, while Subotic marked his return after nine months out with a busy day at the Mercedes-Benz Arena, as the hosts posed a strong attacking threat.
Dortmund may have taken a first-half lead through Henrikh Mkhitaryan, but Kickers saw several chances go begging, particularly through Elia Soriano.
Jurgen Klopp's men added a second against the run-of-play early in the second half as Pierre-Emerick Aubameyang found the net and, although Randy Edwini-Bonsu pulled one back, last season's runners-up netted once more through the Gabon star to progress.
Jurgen Klopp spoke of a wariness pre-match with the third-tier side coming into the game on the back of three games without defeat and he subsequently named a strong side, with the likes of Reus, Aubameyang and Mkhitaryan starting in attack.
After a slow start, Dortmund grew into the clash and Milos Jojic spurned a glorious chance 13 minutes in as he latched on to a loose ball after Adrian Ramos sliced Reus' cross, but the Serb shot wide from 14 yards.
The visitors' superiority began to tell as they took control of possession and eventually went ahead after the half-hour.
Lukasz Piszczek was the architect down the right flank and Mkhitaryan had an easy task to steer the Poland international's low cross home.
Kickers really should have at least drawn level before the break, however, as Soriano inexplicably fired wide of the target inside the area and then Sandrino Braun fired straight at Langerak from close range.
The match continued to entertain at the start of the second half and, after Aubameyang saw an early shot directed on to the post by Royal-Dominique Fennell, Kickers went close twice.
The first opportunity fell to the lively Soriano, who forced Langerak to turn his shot around the post, and then the off-balance Edwini-Bonsu fired at the goalkeeper from inside the six-yard box.
Kickers were made to rue their numerous wasted chances, though, becoming their own worst enemies in the 55th minute.
Fennell played a short back-pass and Aubameyang pounced, skipping past the goalkeeper and coolly stroking into the empty net.
Edwini-Bansu pulled one back for Kickers with 30 minutes left, despite appearing to turn home from an offside position, but Aubameyang netted his second in the 78th minute, tapping in a low cross from the right.
Dortmund's third took the sting out of the hosts' attack and Klopp's men added a fourth in the 89th minute as Ramos raced on to a throughball and calmly slotted in to secure a second-round berth.
