Dortmund have basically already been playing in their 4141/433/4231 hybrid, with Dembele as sort of a no10. All three players you've named committed to defensive duties, Schürrle in particular has a very good work rate and completed 5 tackles according to whoscored (more than any other Dortmund player).
Ginter and Rode would've been the alternatives (Sahin/Kagawa/Götze injured), but both would've been severe downgrades in terms of ball retention compared to Schürrle and Pulisic and even with the two of them Dortmund struggled with Real's pressing intensity.