Yes people do get ratings changed. It is usually a very long process. IT is always based on medical information at the time of separation, not conditions that got worse over time.
I went through the med-board process at the Ft. Belvoir WTU and was not able to get all of the disqualifying conditions in my packet as it was started in Korea.
I apologize for the delayed response--my MEB was finalized on 28MARCH2018 with a DoD rating of 10% and a VA rating of 80% which resulted in a separation with a severance package.