Regarding unbalanced divisions, recall that in the 28-team era there were three divisions in each conference, two with five teams each and one with four (in the NFC, the West had four; I don't remember as to the AFC and I'm not motivated to look it up).

When the NHL had 21 teams, the Patrick Division had six teams and the other three divisions had five each. I think the NBA was long similar since they had an odd number of teams until they added the (now former) Bobcats. MLB was the screwiest due to going with the stupid three-division alignment in each league with even numbers of teams, so the NL had 5/6/5 and the AL had 5/5/4.