Balanced Units - A minimal balance mod for units

It's foolish to rely solely on buffs, as the strength of creatures is relative to each other. You can buff 95% of the weaker creatures, or you can nerf 5% of the strongest. Where is the change minimal? Obviously, in the second case. There are obvious overpowered units, like Sylvan archers, elite crossbowmen, and elite vampires – you can't just leave them as they are. But what if the damage of Sylvan archers was not 8-9, but 20-30, or elite vampires stunned with 100% certainty – would you also need to upgrade the others to the same level?