I agree they do overlap. They are also clumped together as Cluster B traits Personality disorders - Symptoms and causes - Mayo Clinic

I agree the narcissist has no empathy and takes no responsibility for their actions, while the borderline traits tend to look too inward and put undue blame and shame on themselves.

I believe that the diagnoses are moving away from these terms because they all overlap so much, and the behaviors are the focus moving forward in psychology.

If you are asking yourself “Am I a narcissist?”, you are recognizing your bad behavior and are trying to improve, so good for you, keep at it.