I've always found the play -- and Doctor Faustus himself -- much funnier, at least in a darkly humorous kind of way, than it is often assumed to be. Take, for instance, the opening speech, in which Faustus rejects one career option after another, using a good deal of faulty logic in the process. He has studied theology, but he quotes the Bible in a blatantly incorrect way.
Right from the start, then, Faustus can be seen as a somewhat pompous, pretentious man whose pride is fairly laughable. The scenes in which Wagner imitates Faustus further undercut our tendency to take Faustus completely seriously. So does Faustus' later scene with Helen, with her sputtering fireworks.
Finally, in his last speech, Faustus tries to blame everyone and everything but himself for his predicaments -- even including his parents. He continually claims that he "must" be damned, but he never asks God for forgiveness. Faustus can be read as a dark comedy with a definite element of farce.