This series, while R&B fans spin albums by Mariah, Usher and Janet, Ashanti needs more pizazz to compete. On her fourth album, she’s still doing the diva-by-numbers thing, alternating between angry-at-her-man anthems and lovey pleasantry. The shuffling “Body on Me,” featuring Nelly and Akon, and the shiny electro-pop “So Over You” are a step up from her Ja Rule duets of old. But even with A-list producers like Babyface, Jermaine Dupri & Rodney Jerkins, the beats stick to straightforward bounce or subdued ballads. And Ashanti doesn’t offer any more personality: When she coos, R...