The sad thing was that they killed of Dax. I don't know if the actress wanted to quit or not, there are some who claim it was a contract conflict. Whatever, they shouldn't have killed off the character. They could have had her sent on some mission somewhere (maybe to find Voyager) and brought in Ezri without the "Dax" connection.
I seem to recall an interview with Terry Farrell where she says straight that she would've prefered Jadzia to be transfered rather than killed off... she said it was affection for the character, but also I think she'd have prefered it because if this Becker thing didn't work out she would still have had some
life-line to returning to DS9... but it's a well known tactic used by some Hollywood producers, to kill off characters whose actors walk from their show, precisely so that their bridge backwards gets burnt behind them. Perhaps Farrell did
come to regret her decision to jump on Ted Danson's new show instead of staying on the Star Trek ticket one more year. Or maybe she figured, hey, it's only one more season anyways so what the hell.
This "kill off the character because the actor wants to leave" trope is so common in TV-land that the occasions when it isn't used, like when Detective John Kelly in NYPD Blue was allowed to stay alive (off-screen) even though David Caruso was being an asshole and leaving the show under a cloud, are all the more notable.