remember, brake fluid loves water (hygroscopic?) & water and air are easier to compress than brake fluid. It's possible that if you had a leak then air or water or both have entered the system.
On the other hand, we have a Renault bus at the depot which many refuse to drive due to the nature of the brakes - mechs have changed everything but it's a frightening experience trying to stop when you're not used to it.
As to your OP, it's not, normally, a good idea to change a drum/disk without also doing the shoe/pad at the same time as uneven wear/faults on one can impact on the other, especially these days as linings seem much harder & drums/disks seem much softer.