First of all. How is not adding the actual MUSIC of it not part of being an artist? yes producers are artists.
definition of artist:
a person who works in one of the performing arts, as an actor, musician, or singer; a publicperformer: a mime artist; an artist of the dance.
I would consider a producer a musician. But really it is not too hard to understand how adding guitar or whatever to rap vocals is part of being an artist.
How is biggie a producer????