I don't think Ferraro helped or hurt Mondale's chances in 1984.
Having said that, I think the manner in which she was selected reinforced negative stereotypes about the Democrats. Feminist groups publicly threatened Mondale that they wouldn't support him unless he picked a woman as his VP candidate. Mondale was reportedly furious because he had already planned to pick a woman, and now because of their public threats it appeared that he was giving in to blackmail from a special interest group.
The problem with Ferraro was that she was picked only because she was a woman. A male three-term congressman from a New York City borough would never have been considered, and everybody knew it.
Mondale had little to lose by rolling the dice and picking a woman for his VP candidate, but he didn't end up gaining anything either. I find it surprising that a woman hasn't been picked in the 20 years since Ferraro.
What you say about the Dems is right on, and I know personally that the #2 choice after all the vetting was done was the African American mayor of LA, Tom Bradley. He was determined to pick the someone from an oppressed group.
