You had written:

"...ego state is quite different, to me. The ego acts a bit differently as a whole than a "complete" personality... the ego is a defined aspect (and usually a selfish, often negative one lol)."

In most contexts, as I said before, "ego" does NOT refer to "a selfish, often negative" part. I'm not sure why've you have come to that conclusion.

As for dissociation, ego states exist irregardless of levels of dissociation, but ego state theory, as it has been developed for use with DID and DD, is intricately tied to the study of dissociation. It would be useless to discuss ego states, in most clinical contexts, without discussing dissociation. Why exactly do you think ego states have nothing to do with dissociation?