... It still also kind of bugs me they never seemed to have a science officer again, but then again they never seemed to need one, either.
Yes. Technically, they should have had a science officer come in to replace Jadzia. But the focus of the show had shifted from one of discovery and wonder to defense and combat. Along with combat comes stress and psychological trauma, something they got to explore a bit more by having a counselor replace the science officer.
I'm sure they considered replacing Jadzia with a science-officer host, continuing the character in the same role as the previous six seasons. But since their story-telling had changed, they probably considered a number of alternate positions for the new Dax to fill. Counselor was probably the most obvious to tell stories about the invisible scars of war.
So we got Garrick's runaway claustrophobia in "Afterimage", an unsuccessful effort to help Nog in "It's Only a Paper Moon", and her incisive remarks about the Klingon Empire in "Tacking Into the Wind".
Actually, it's disappointing that there weren't more signs of her helping out with post-traumatic stress among the crew. All-out war was rarely explored in Star Trek
, and Deep Space Nine
remains the only effort to do so in a detailed manner. Lacking writers with any first-hand experience in the subject, it's surprising they did as well as they did, but I never felt completely satisfied with that aspect of the show.