Etta suffered exactly because Diana had never had a secret identity.
The thing with volume 3 is that it never got around to establishing Diana's life out of costume. But perhaps her the neighbours around her apartment were grateful Giganta never turned up and stomped the building flat.
On the contrary - Robin's father survived as long as he did because of the secret id. He was only killed at all because the wrong person knew the secret, which just highlights the need for a secret identity to be closely gaurded. It did, however, raise the issue of protecting the secret ids and what is and is not acceptable. For example, mindwiping the villains who stole the JL's bodies in an earlier adventure. Which personally I have no problem with.Identity proved exactly one thing: Brad Meltzer is not very good comicbook writer.
By the way, speaking of Identity Crisis, Robin having a secret identity didn't do his father a lot of good. Sue Dibney was killed by a civilian friend. And her being raped was in no way at all the fault of Ralph not having a secret identity. It's not as if Dr. Light came after her in her own home. Or came specifically after her at all, actually.