I think Neumann either does not have enough talents to build excellent headphones,
If you're concerned about talents, Axel Grell was part of the team that designed the NDH 30 (
source). He was the guy behind the HD6X0 and HD800.
No marketing, no community shake-ups
That's just a different STP (Segmentation, Targeting, Positioning). Neumann's focus is pro audio instead of audiophiles/casuals. On youtube, you'll see there are a lot of talks about the NDH 30 but it comes from studio oriented channels.
rumors of re-using parts from other (Sennheiser) headphones....
Even if they have similar DNA that doesn't mean much. In addition, you have to consider earphones and headphones as an acoustic system versus just the transducer. There are so many other variables besides the transducer and its tuning, all of which affect the resulting sound (coupling, resonators, materials, nozzle scope, filters, back volumes, and so on. Even the most minute difference can wildly influence the output.
A good analogy is an automotive engine, where its performance can be tuned individually, but the overall experience of driving the car is affected by tires, weight distribution, transmission, feedback, stance, etc. For example, the Audi TT and VW Atlas use the VW MQB platform but are entirely different vehicles.