They could;

1. Allow miracle to be cleansed but change the limit break to be a beam miracle instead of a beam stun, and swap miracle 25 second with a regular single target stun every 25 seconds. This would make it so that miracle is a limit break ability.

2. Give miracle of nature a cast time, duh

Any of these changes would likely upset a lot of folks who have been carried by the job for all this time but still be completely manageable for any minimum skilled white mage.