I agree with that they say and how it should be divided
but I would put Run DMC in the first category. Because Run DMC didn't fit with late 80's artist. They fit with Flash and Five, hell they took shots at one another. They were pretty washed by Tougher Than Leather, but had stuff like Run's House and Pause. Everyone was shocked with Down With The King, which was a testament to Pete Rock. Rap had changed that fast from 84 to 88 that they were ancient by 25. Looking back it that's crazy.
And it's hard for me to leave Kool G Rap off a list, when 30 years later he still sounds like he fits. Which shows how ahead of his time he was. Plus he helped birth Nas and Pun.
DOC being mentioned