There is exactly the same resistive losses with DC as AC. It is a simple Ohm's law calculation.
What IS reduced is inductive loss. That is not really a problem where the conductors are physically separated as they are on a typical land based transmission line and only becomes a problem where the conductors are bundled together as in a submarine cable.
If Tas were to export power to Vic, for example, they would use DC. There would be a secondary advantage that the two grids would not need to be in sinc but you would need big rectifiers in Tas and big DC/AC inverters in Vic. Not a task to be taken lightly.
