NIKNAK -
You say that other operators have ditched MAN-DND "for exactly the same reasons" (as Eastern). I suggest that you are mistaken in this. If memory serves me, the only other operator on this particular route in recent years was Business Air, now a part of BMI. They served MAN-DND successfully for a number of seasons; aircraft often routed ABZ-DND-MAN which no doubt helped the viability of the service, however the DND sector appeared to be well supported. I believe that GNT eventually dropped the route to release runway slots at MAN for the launch of a MAN-BFS operation which was considered a priority at that time. Part of GNT's business was the provision of connecting traffic onto the networks of Lufthansa and SAS and they wanted a BFS connection. The DND rotation was the obvious flight to make way, as a GNT non-stop ABZ-MAN also operated at similar times of day; if the non-stop service had been sacrificed in favour of the DND stopper, BA would have gained a competitive advantage on the ABZ-MAN sector. Business Air dropped INV-MAN at around the same time. I think you will agree that these circumstances are quite different from those affecting Eastern today.
I suggest that Eastern's disappointments on the DND-MAN route are more likely to be related to the relatively high fare structure which the company offers. Eastern fares (in my opinion) appear to be pitched towards the business end of the market only. This is not a criticism; simply an observation that leisure travellers are likely to by-pass such fares in favour of significantly cheaper deals on such routes as EDI-MAN. Perhaps Eastern should consider an INV-DND-MAN routeing instead?
If anybody can correct or otherwise explain the circumstances described above, please feel free to do so.