Let me comment only on the question you raise about Diop's standing among
African historians, leaving aside the issues about African philosophy.
Diop was a nuclear physicist by training, not an historian. His use of
sources is extremely selective, uncritical and a-contextual, and he lumps
material from very different periods together. One can't deny, however,
that his work has been influential and it is important for its resonance,
especially in the US. And, of course, Bernal has followed up on Diop's
ideas in exhausting detail, but even his more careful attention to
language and texts has been soundly criticized by scholars such as Mary
Lefkowitz.