I have come to object the idea of a ‘balanced’ drink, although I still lazily refer to a ‘perfectly balanced cocktail’ when I drink something I feel couldn’t be improved upon.
Martin’s Old Fashioned example is perfect in that respect. I tend to use the Daiquiri: a Daiquiri where the sourness of the citrus and the sweetness of the sugar are ‘balanced’ is a flat drink, which explains why a lot of Daiquiris are not great.