There are two factors involved in population growth; birth rate and death rate. Often people forget about the former. Some species of whale can live hundreds of years, but they dont become over populated because they only produce a few off spring after 100 years of life.

I do not think we need an increased death rate from diseases to balance our population out, but rather the evidence has shown that the birth rate and number of offspring of a species will natually adjust to fit the death rate.