Donne's religious poetry frequently turns into a one-on-one grudge match versus death. In Holy Sonnet 10, he declares, "Death, thou shalt die." Well, in this poem, death dies. Everyone who has ever lived is brought back to life, but not before Donne reminds us of death's power by listing all the different ways a person can die.
The speaker does not ask for more time so that he may mourn those who have already died. He wants to mourn his own sins.
In his statement that the fires of the Apocalypse will "o'erthrow" sinful people, Donne shows that there is a kind of death in the Christian afterlife.