One might argue that "The Emissary" and "Birthright" aren't necessarily stories that are important to the fate of the Klingon Empire, not in the sense of the other episodes listed...
* "Heart of Glory" introduces the Kahlessian "honor movement" and the internal Klingon strife; it also outlines the relationship between the Empire and the Federation
* "A Matter of Honor" gives us the backstory of the second officer's father and some idea on how mainstream Klingons define honor and view the Federation
* "Sins of the Father" lays the groundwork for the whole political game involving the Houses of Duras and Mogh
* "Reunion" brings that to a dramatic turning point
* "Redemption" shows where this gets the Empire
* "Rightful Heir" solidifies Gowron's rule
In addition, "Mind's Eye" is an important lead-in to "Redemption". But "The Emissary" and "Birthright" are mainly Worf stories rather than Empire ones. "Firstborn", too.
Timo Saloniemi