for evolution, why is it important that we have “oddballs” outside the “ideal/average” size range?

for starters who decided that average is ideal? well... evolution consist in very slow changes that come from mutations in the DNA of all living things, and when this changed creatures (oddballs) happen to have a slight advantage over the other members of their specie this mutation stays and over time with more mutations whole new animals or plants are born. that's why "oddballs" are probably the most important part of this process.

Maintaining genetic variation, I suppose.