I would question the gas shocks.
Remove them both and set the car down without them and see if it improves. Even drive around the block without them to settle everything. The gas pressure may be holding it up. Or could the shocks be overall too long and are bottomed out.
I had one go out on an old Mustang I have it went to full extension and would not return.
Only way I could see the factory leafs being too high is if car was up on stands with the rear hanging for a verrrry long time.
Mike