did the weight include the golf bags or was the trunk also full with 4 golf bags weighing another 100 kg? You really might have overloaded the car. But seriously, you check the shocks by pressing down on the corners as hard as you can and then watch the bounce. It should just come up, as the shock stops the spring from overshooting and then going down again. You can also have somebody drive the car on a bad road and watch from the side how the tires bounce. Compare it to a new car. I often see at stop signs with bad roads the cross-traffic go by and point out to my wife if a car has particularly bad shocks.
The fact that yours are oily also indicates they are bad.
And with 194,000 kms over Aussie roads some rubber parts of the suspension are probably shot, too.
As Steve said, have ride height checked and look what is all in need of replacement. And yes, softer tires and tire pressure also play a part, however more at the beginning of the suspension travel, not the bottoming end, which you seem to experience.