The triumvirate paradigm doesn't work nearly as well in DS9 as it does in the other Trek series. First, there's the whole ensemble cast thing. Second, less of the drama takes place in single locations. Nonetheless, it feels like there may have been some attempt to elucidate a three person grouping at the series inception: Sisko and two advisers/confidants. Of the remaining men in the cast, no one was close enough or important enough to guide Sisko's decisions. On the other hand, Kira was a necessary adviser and Dax was a long-time acquaintance and friend. Now, the paradigm doesn't hold up well over time. The characterization of Dax was off, and the actress wasn't always up to the task (by her own admission). Dax makes a great comeback in season 6. In the meantime, Odo and Worf are much closer to Sisko, but their personal stories take over. Even if Dax fell out for a while, it still seems that the series was intended to look like a man of color and two women leading the action, making it more progressive than other versions of Trek.
I don't really think any of the series had a particular strong grouping of 3 characters beyond Kirk/Spock/McCoy in TOS. Picard, Sisko, and Janeway all had unique relationships with members of their crew, but I can't think of any that I would lump together like the "Big 3." Archer, T'Pol, and Tucker come close, but they're the only ones.
^I think that the other series had strong triumvirates even if the casts were more balanced than the original series. Most major actions/decisions were made by Picard-Riker-Data, and clearly Riker and Data were Picard's closest advisers on official matters. The same could be said of Janeway-Chakotay-Tuvok. It's not that other crewmembers did not matter, or that the captain did not have personal relationships with them. It's that some crewmembers had the captain's ear in the way that others did not. Indeed, my proposed DS9 triumvirate (as weak as it was) resembles the other series: one leader (Sisko, Janeway, Archer), one long-time friend (Dax, Tuvok, Trip), one honest, dedicated adversary that has been foisted on them (Kira, Chakotay, T'Pol). Thesis-antithesis-synthesis: Hegel would be proud.
I could see Sisko and a Bajoran officer, here Kira, working closely together. Otherwise, Sisko would work with other Starfleet personnel--and the Prophets, of course.
For me, only TOS has the "big three" thing going on with any significance. Maybe TNG has a bit of it with P/R/D, but the other shows don't come close. Certainly, DS9 would be the Trek that shys away from the "triumvirate" format the most.
DS9's crew was always given more functional roles than in the other shows. That is, in other shows, when they have a mission they just throw together all the main characters regardless of whether their position is mission appropriate. In DS9 more so than other series the characters appropriate for the mission are present, with the glaring exception of Kira's constant presence on the Defiant. So whereas TOS and TNG tended to have all stories flow through the central command structure, DS9 would take groups of any two or three characters in isolation and write the story through their eyes. And Odo and Quark are the real main characters anyway. And Voyager's triumvirate was Janeway/Doctor/Seven.
Er ... the Doctor is the more important character as the series goes on, but we seldom see Janeway going to the Doctor for command decisions. ETA: perhaps I should be more precise: I'm not so much interested in which actors (and their characters) occupy the premier space on the marquee, but rather how the characters interact with one another.
The reason the original "Big 3" works for me, though, is not just Spock and McCoy's relationship with Kirk, but also their relationship with each other. They make up a trio. Janeway is close with Chakotay, and Janeway is close with Tuvok...but Chakotay and Tuvok barely have a relationship at all.
It's not the same in DS9 and Voyager though because the three highest ranking people on the ship are not the people who are a cohesive team on away missions. Kirk, Spock and McCoy were out in the field together. That can't be said for the main characters of any other Trek show. Picard and Riker made decisions on the bridge, but it was more Riker in command on away missions with Data and Worf, and whichever character the episode focused on was the primary decision maker. Dax's advice to Sisko was usually given as a personal check rather than a professional check, and Kira didn't have the same relationship with Sisko because she was the advocate for Bajoran interests. Again, whichever character the episode focused on was the decision maker. Same with Voyager, they didn't beam down to the planet with Janeway, Chakotay and Tuvok. Chakotay was a lapdog except when Janeway was acting especially crazy and Tuvok was more like Dax.
Now, if it had been Curzon Dax, I could see a DS9 "big three" between him, Sisko, and Kira... Curzon Dax (id) Kira (ego) Sisko (super ego)
Bad Thoughts: Seeing as Jadzia died at the end of the 6th season, in your view was Ezri a part of the Big 3 during the 7th season?
Yes, you're right - there's definitely a vibe in ENT. For some reason, I didn't consider it when I made my post.
Given that my observations only concern the first 5-10 episodes, Ezri is superfluous to my question. Moreover, by the "final chapters" arc, most of the characters are working individually. I think that Kira and Odo are taking the lead in the action aspects of the episode, but they are not forming a working unit with Sisko. Perhaps I should, once again, be clear that there is no clear triumvirate, just the outline of one in the first season.
In my opinion, the "big three" concept is about as antiquated as standalone episodes. DS9 gave Trek storytelling a swift kick in the pants by eschewing both for an arc and ensemble cast. It's Only A Paper Moon focused on two of the guest stars (Nog and Vic Fontaine). That's some outside of the box thinking.
I think DS9 is defined by pairings that interact with other pairings. Sisqo and Kira. Odo and Quark. Bashir and Obrien Worf and Dax.. Nog and his father. Weyune and Dukat.