Most of that admittedly vast list of managers have 'manager' in their title as a result of the contract versus EBA process established some years back. Before that most of them would have been ops support specialists, or some other appropriately demure title, and most would have been paid as part of the relevant ATC or engineering awards.
Having said that, I'd have to agree that the number of support staff or managers is disproportionate to what the organisation actually does (air traffic control for those who've forgotten) and apparently and obviously repetitive if the titles actually represent what the occupants of those positions do for a living.
You'd have to ask the question - if you outsourced the management of the primary function of Airservices Australia - that is, air traffic control and managing the equipment that lets those controllers do their job - how many managers would be employed? I suspect no more than twenty.
Good luck to the new guy at Sydney - all alone from a foreign environment with no support and 150 miles from that wealth of management talent in Canberra.