I don't know which airline this concerns, but in general I believe this issue has a lot to do with the size of the organisation.
For instance, in a v. large airline, ops duties are divided and specialised for efficiency. There are probably enough flights to justify someone whose duties only concern slot management. But then in a tiny organisation one person has the time to do everything from flightplanning to booking crew hotels (and time to get good at all duties).
Business management studies have proven the efficiency of division of labour in a large organisation, but this loses effectiveness if the company is downsizing.
Sidsnstars - as long as your colleagues have the time and the training, don't underestimate a good dispatcher/controller's ability to adapt and become good at any duty!
End of lecture!!