I was playing around with this mon a week back. I came to this exact set except I would alternate between a Kasib or Babiri berry. Babiri for the tech against the Sub-NP Steel/Dark move Hydreigon set that shot in popularity and is a standard set now. Kasib was for unsuspecting Dragapults (which is a crazy mon with a crazy speed tier). In both cases, Rapidash would win the Dynamax war.
This mon isn't terrible. It has good speed and attack. It is just kinda frail and simply outclassed. However, I think it will have a place maybe in RU or NU.
Dynamax allows it to set Misty terrain and beat walls (in particular while I was playing GCorsola) after an SD - in particular those that tend to go for burn initially.
I found that Wild Charge (for Gyara and Corvignight) and Low Kick (for Ferro and Exca) is the best coverage.