As someone who is dark skinned and is still waiting for proper representation of the African goddess Storm, I find issue with Shipp's casting.
Well, therein lies your first problem: Storm is not an "African" Goddess. She was worshipped there, but the girl is from Harlem. Her mother is of natural African descent, but her father is American and she was born in the States. Therefore, Storm is African-American, first and foremost. And she grew up in Cairo, Egypt. So these facts alone show that she could be really any complexion as Egyptians (which coincidentally is partly my own personal heritage) come in all shades of color including the fairer complexions. Also, even if her mother was dark-skinned, her father could've been any shade as he came from the cultural melting pot that is America.
This is why Storm is shown in a variety of complexions throughout the decades.
For a moment, FOX had it "right" with Storm in the first X-Men film. But after that, the make-up and costuming department seemed to go out of their way to Americanize Storm's appearance--she dropped the accent, and her hair was either blond or streaked and Halle's facial make-up was lightened as well. At least with Alexandra, there seems to be a concerted effort to bring the character back to its roots.
This is FOX. We should be glad they didn't cast a white actress to play Storm this time around--they're really into that these days.

*coughJessicaAlbaSueStormMichaelBJordanHumanTorcahcough*