I thought that Jax was actually talk about Brenda whose life did get so messy because of Sonny that she had a nervous breakdown that Jax had to help her get better. But then they couldn't do the comparison to Valentin and Sonny about being good fathers because Brenda going back to Sonny had nothing to do with him being a father.
Carly's lowest points in her life were when she thought Michael died (he didn't), Michael was in irreversible coma (he recovered), suffered her own psychotic breakdown (she recovered and eventually got involved with Jax) and finally when she lost Morgan (whom we are all expecting to come back from the dead). Despite all the trauma, Carly has been able to live her life and doesn't really need Jax to save her from it. He really can't fix anything for her because for the most part Carly doesn't see that anything is broken with her life.