“I find it absurd that I should be responsible for the failed waterproofing.”
It’s written into laws in Victoria, specifically the “Subdivision (Registrar’s Requirements)
Regulations 2011”, which means the OC can’t change it even if they wanted to.
As JT states, the OC could vote to repair lot property. That’s going to be unlikely unless most balconies are affected.
And even then, if the repair cost was raised by a special levy, the OC is required to apply the “Benefit Principle” which means lots that benefit more contribute more. So it still might mean that you effectively have to pay for your lot’s repair.
Best to try to a building warranty claim. But it might be too late for that.