The difficulties of creating a balanced diet for cats are greatly underestimated. The problem being that dietary deficiencies don't show for weeks, months, or even years... but in the end they will cause problems such as weak bones that are prone to fractures, heart disease, or blindness. The crucial thing when feeding dry food is to encourage the cat to drink plenty, and if you do decide to change diet, do so under the guidance of a veterinary nutritionist.