Paul Laurence Dunbar wrote much of his work in an African-American English dialect of the Antebellum South and also, on occasion, employed the Midwestern regional dialect favored by his friend and patron James Whitcomb Riley. The elevated diction and formal structure of "We Wear the Mask" is very different from either. The language of the poem is tragic—with "torn and bleeding hearts," "tears and sighs," and "tortured souls." Christ is even invoked as the witness of suffering.
Dunbar never says who "we" are, which means the question is open to interpretation, but in the context of the poet's life and work, it is overwhelmingly likely that he is referring to African Americans and their position in American society. The primary reason for his use of this structure and language, therefore, might be to give dignity and even grandeur to the struggles of African American people.
There were all too many detractors willing to cast aspersions on the intelligence and intellectual attainments of African Americans in the late-nineteenth- and early-twentieth century, which was when Dunbar was writing. Many were incredulous that a black man could aspire to a career in literature at all. To have written in-dialect would have served to reinforce their prejudices, and Dunbar wants to give such people no excuse to write him off as he articulates the tragic position of his race.