I think it is best to balance around how units are played at the top level.
If you try to balance for low-rated players, what do you think would happen? High-rated players would figure out how to exploit the new units. The meta would change. Everyone else would try to copy what the high-rated players do. And then things would be broken again for the low-rated players.
The balance will always be "broken" for low-rated people. 99% of them would win 10% more games if they just made tiny, tiny changes to the way they played.