I think it is unfair to hit on Nicole deBoer
for not being other than what she is. Clearly she was asked to fill out the small remainder of the series when her predecessor, for whatever reason, left.
It ecsapes me now, whether it was Hans Bemmler or Richard Manning was the producer of the final episodes of Deep Space Nine. Both have extensive experience in Canada producing the science-fiction which is becoming Canada's contribution to world Television.
They were, if memory serves, producers on Beyond Reality. DeBoer was a regular on that series.
But something was happenning in the progression of hosts for the Dax symbiont. Curzon Dax (I guess that's how its spelt), was a mentor figure for the hero of the series, Benjamin Sisko. And all that meant.
That was not in the current (though now, sadly, terminated) series, though possibly available for a "back" series. If you look closely, all the other characters were cast, and written to be less strong (I hesitate to say weaker) than Sisko. There is the height thing. There is the voice thing. Even Jadzia Dax, for all her intelligence, strength, and experience--how many women could be a match for Worf? (Though there was that fling with Ezri.)
So, Jadzia is Sisko's equal, but no mentor. It seems sometimes the opposite. And for Ezri, well, the two-parter that was her debut, all of the characters were there merely to reflect the ordeal of the undisputed hero, Benjamin Sisko.