I have to say that this is an interesting read. The thing is that what has happened to DSA is exactly what was predicted by the then LBA director, and others, and formed part of the objections to the airport at the public enquiry. It was, as I recall, stated that the only way DSA could succeed was if it could entice passengers away from MAN, EMA, LBA and HUY, but that it could be doomed to fail because of its relatively remote location, which is too far away from its major catchment area - Sheffield. As posted earlier by Muddycoffee, Sheffield folk can reach EMA quicker, especially those living to the South of the City. Those living to the West can easily get across to MAN, and those to the North can get to LBA reasonably quickly too.
Had Tui not take a policy decision to try their luck at 'minor' airports such as Bournemouth, Coventry and the new DSA, I suspect Donny would already have failed completely. After a bright start, it has been downhill steadily since and the fact that Thomson are now showing signs of heading back up the A1 to LBA (still in a minor way, but nevetheless a complete change in policy with routes to Palma, Corfu, Dalaman, Sharm el Sheikh, Enfidha and Paphos), the situation appears to be rather bleak.
What has happened though is what the directors of the surrounding airports said would happen. So can DSA succeed in the longer term? Personally I think it is battling too many competitors, all within reasonable travelling time of Doncaster and Sheffield. MAN is growing again, EMA appears to be pulling out of a dodgy period and LBA is poised to grow rapidly after its terminal development. DSA is too reliant on charter work - always a volatile market and the first to suffer from consolidation when the times get tough - which is what has happened to DSA over the last 2 years or so, with their based TOM fleet shrinking year by year. With the exception of Wizz, every other scheduled service has failed . That, I fear, is DSA's real Achilles heel. Airports in this country rarely succeed if they can't hold down a reasonable number of scheduled services.