Major League Baseball playoff seedings are based on two leagues, each with four to six teams (has varied over time). For each league the three division winners are seeded 1-3. I like MLB playoffs because even today 12 of 30 teams (and even less in previous years).

1st seed = 9 championships
2nd seed = 3 championships
3rd seed = 3 championships
4th seed = 4 championships
5th seed = 1 championship

2022 Houston Astros (1)
2021 Atlanta Braves (3)
2020 Los Angeles Dodgers (1)
2019 Washington Nationals (4, WC)
2018 Boston Red Sox (1)
2017 Houston Astros (2)
2016 Chicago Cubs (1)
2015 Kansas City Royals (1)
2014 San Francisco Giants (5, WC)
2013 Boston Red Sox (1)
2012 San Francisco Giants (3)
2011 St Louis Cardinals (4, WC)
2010 San Francisco Giants (2)
2009 New York Yankees (1)
2008 Philadelphia Phillies (2)
2007 Boston Red Sox (1)
2006 St Louis Cardinals (3)
2005 Chicago White Sox (1)
2004 Boston Red Sox (4, WC)
2003 Florida Marlins (4, wC)

1st seed winning almost half the championships is pretty good. 2nd and 3rd seeds (i.e. other division winners) winning close to 1/3rd of the time is not bad. Lower seeds winning 25% of the time is much too high.

Here I would implement unfairness: whenever a division winner matches a wild card team it goes from 4-3 series to a 5-2 series (i.e. division winner gets five home games). You still get 12 playoff teams and in baseball winning on the road is not as hard as in basketball so 5-2 is not impossible for the 2 team.