Ezri is my favourite character, so I definitely don't agree on 'worst.' There are a range of options for that.
I would have really liked them to change Daxes halfway through the show. More Ezri for me. Less rush to introduce her in S7 for others. Win-win.
Jadzia suffered from inconsistent writing; rather than contain the serenity and wisdom of age at the same time as youthful enthusiasm, she switched between. And then she turned into a spotted Klingon.
Ezri was far better written for exploring what it means to be a joined Trill, a species far more interesting - and far less already done - than Klingons.