G’day Centaurus,
Am only a humble non-flying GA pilot nowadays, but in a C402, single engine, limited panel, NDB circling and missed approach was mandatory if you wanted your instrument rating to continue. So at least the GA examiners thought it was worthwhile.
Then again, most of them were ex RAAF except for two that I can remember.
And if you believe in the “train hard, play easy” which I do/did, it was worthwhile (but then again, I never had to do it for real so I cannot say if it was effective).
Never had to chase the ‘aural null’ stuff but on one occasion I started one of those DME homing debacles.