It is based on the original balance. Part of me wanted to change that, another part didn't. In the end, when it comes to the units balance, I decided to keep it semi-original.
Yes, you can edit the damage as well.
Yes, you can edit yaml files if you want to balance the game yourself :-). That's the point of OpenRA modding.
By the way, I've got a new version coming "soon". You can give a try: