In my opinion, it was a huge mistake to even revive the character of Dax for the final season. No matter who they cast, whether it be Nicole deBoer or Angelina Jolie, and no matter how good or bad they acted, there would not have been sufficient time to develop the character, and what development they could do would distract from the Dominion War arc they were trying to wrap up. And that's exactly what happened. There were at least five episodes devoted directly or indirectly to the development of the Ezri Dax character, who would only be on the show for a year, and those five shows could have instead focused on the war. That way, the finale wouldn't have been as rushed as it was.
And it didn't help at all that Ezri Dax was basically a whiny little kid.
And it didn't help at all that Ezri Dax was basically a whiny little kid.