You probably have to go back to the '70s. Baltimore had 4 20 game winners in 1971. Palmer, Cueller, McNally, and Dobson. They still lost to Pittsburgh in the series.
The 1966 Dodgers had Koufax, Drysdale, Osteen and Sutton...and lost to Baltimore in the series.
1972 A's featured Hunter, Holtzman, Blue Moon Odom and Vida Blue....