5 nm is all you need to avoid them totally, like 2.5 nm either side of where they are dropping. Struth, how hard is that?
Pull out the Melbourne VTC and have a look.
2.5 nm one side and you infringe controlled airspace (or at least the tolerances for your planned track). 2.5 nm the other side and you are 2.5 nm offshore at 1500 feet.
There are 4 VFR approach points for Essendon and Moorabbin within 2.5 nm.
The coastal VFR route is marked literally right through the middle of the drop zone.
It does seem like a dumb place for a drop zone.