I replace mine every other yr. They always have the melted appearance at the end as yours does. I think that is normal wear. The 2 grooves are more than what I see normally.
You got it apart, put in a new kit.
I doubt it's needed, but I always sand the mold parting lines smooth on the inside too. Figure might as well eleminate those sharp edges to keep them from cutting the new impellor. Only takes a minute to do.