I actually find that thought offensive. There's a legitimate problem with lighter-skinned people of color getting crap both from racist white people as per usual, but along with darker-skinned people of their own race for "not being black enough", like it's a choice they're making.
Diversity is diversity. People of color are people of color, regardless of the exact shade. How dare you try to make that distinction. You don't get to say that Lupita N'yongo is somehow more diverse than Halle Berry because her skin is darker, that's problematic as hell.
So far this cast has actors of Pakistani, Mexican and Asian descent. I'm sorry that you don't consider their ethnicities to be real enough for you. All of those people are POC whether you think they're dark enough or not. Those people are diverse whether you're okay with the amount of melanin in their skin or not.