I have been watching DS9 trying to catch up on all my Trek history and I had thought that the reason why the KDF had the joined trill was because of Jadzia and Worf but at the end of season 6 jadzia is killed. Now I still have to watch season 7 so maybe my answer is there but I don't mind spoilers so can I get the canon reason for the KDF having Joined Trill or was it just to even things out.
I have a trill KDF so I'm not trying to be hypercritical here or anything just a question of curiosity.
Maybe some Trill/Symbionts (not wanting to go extinct) feel the Empire is better suited for taking on all these agro species flying around the galaxy, since the Klinks have outted a ton of Undine and the Feds keep gettin' punked by them.
Well I don't know the specifics... but BEFORE the Dax entity was joined with Jadzia, it was in a guy named 'Kurzon". The reason Sisko calls Jadzia 'old man'. Apparently Kurzon is well liked by Klingons, and even General Martok knows and respects Kurzon. I think he was an ambassador, or some kind of liason to the Klingon people.