The phrase "heavily dependent on" is correct and usable in written English. It is commonly used to emphasize that something is completely reliant on something else, or that a certain result depends entirely on a particular factor. For example, "The success of this project is heavily dependent on the cooperation of all the team members.".
Actually, the two halves are heavily dependent on one another.
Sixty-one poor nations heavily dependent on American aid have signed similar agreements.
Both are heavily dependent on public spending.
We're heavily dependent on legal aid.
Peru's economy is heavily dependent on mining.
The Philippines is heavily dependent on imported fuel.
Its economy is weak, and heavily dependent on state spending.
Since I tried Ludwig back in 2017, I have been constantly using it in both editing and translation. Ever since, I suggest it to my translators at ProSciEditing.
Justyna Jupowicz-Kozak
CEO of Professional Science Editing for Scientists @ prosciediting.com