Is there a need for teaching faculty in Germany?

In the United States and several other countries, it is common practice that introductory lectures are being held by teaching faculty, i.e., lecturers and teaching professors. In physics departments, this includes classes such as "Introduction to Experimental Physics" (classical mechanics, electricity and magnetism, thermodynamics, optics). Higher-level classes as well as electives, however, are often taught by "regular" faculty who only devote a certain fraction of their working hours to teaching while also being involved in research and service activities. By contrast, in Germany also the introductory classes are taught by the aforementioned "regular" professors, and typically no additional teaching faculty are hired by the universities. Obviously, there are advantages and disadvantages to each of these two distinct approaches. For example, hiring teaching faculty leads to additional costs for the university, but on the other hand one might argue that, on average, their higher enthusiasm for teaching and the fact that they solely focus on their classes leads to a greater success in the students' learning experience. Unlike "regular" professors who may regard teaching as an obligation, teaching faculty usually have a strong passion for teaching and do not have many other duties that would distract them from preparing their classes. 

I am not aware of any scientific studies on the comparison of the two aforementioned approaches (please let me know in the comments if you know such works), but I am convinced that teaching professors and lecturers are more suitable to teach introductory classes and ultimately students can benefit from the pedagogical skills, enthusiasm and experience of the teaching faculty. I understand that for higher-level elective classes on very specialized topics it can be beneficial that the instructors themselves are involved in current research efforts in the respective field. This allows them to convey cutting-edge research contents to the students, whereas teaching professors and lecturers may not have this up-to-date knowledge. However, this depends on the individual case and there certainly are electives that can also be taught be teaching faculty. 

In conclusion, I would really like to see a transition towards introducing and hiring more specialized teaching faculty staff in Germany in order to offer the best possible and effective learning experience for students. Since I am currently involved in the organization and preparation of an introductory experimental physics class, I can clearly see how high the workload is and how challenging it can become to carry out research in parallel to such time-consuming teaching activities. Moreover, from my personal experience as a student, I have seen many professors who significantly neglected their teaching duties and did not deliver high-quality lectures. I will never forget, for example, one professor who stated at the beginning of the weekly Wednesday-morning lecture at 8 am: "Sorry folks, we have been analyzing super exciting data from a beam time and therefore I have not slept a single minute last night. I apologize in advance if the lecture today will not be to your full satisfaction." I appreciated the honesty, but nowadays I just hope that such scenarios can be avoided, for example, by hiring teaching faculty with a passion for teaching and no other obligations in their daily work.