Nah, the worst DS9 character would be either Zek or Ishka.
Ezri could definiitely have been handled better in season seven though. I think she was better written than Jadzia, as it was more interesting to see a Trill joined that wasn't ready for it. She stole a lot of screen time by being the new girl, so I would have preferred her as a recurring guest, or even for Jadzia not to have been killed in the first place.
Or kill Jadzia off in season four and let Ezri develop at a normal rate.