In Victoria, waterproofing, even of external areas (like balconies), can be an owner responsibility. It all depends on exactly what is causing the leak – and where. Has the exact source of the leak been determined? If not, the OC should be at least establishing that.
“Poor housekeeping” – what does that mean? That gutters are not being cleared? That’s probably an OC issue too if the gutters are Common Property.
What ‘work’ are you proposing to get done? If it turns out to be a building defect, the cost of repairing the defect will not be covered by the OC’s insurance, but the cost of repairing any consequential damage due to the defect should be.
I don’t know why an insurance claim should cost anything to make. It’s either knocked back or accepted with a possible excess to pay.