My point with all of this is that different people will set different limits and we can't assume we agree on them. I was at some folks house for Halloween that did their garage up as the "Dead Disco" they had a few severed legs, martini glasses filled with severed fingers, punch with eyeballs, etc. Also one animatronic dancing zombie.
In my opinion horrorcore is closest to reading a horror novel. Although there are of course music videos, and some of those are way way over the top, but with just listening to the music and rapping you have to imagine the situation in your mind much like reading a book.
Compare this aspect of horrorcore with ultra realistic slasher horror films like the Saw movies: