With regard to the statement, "Death is a common theme in Hardy's poetry," I would have to agree .
One source cites:
[Hardy's] works are often deeply pessimistic and full of bitter irony, in sharp contrast to the prevalent Victorian optimism.
As a Victorian author confronting the changes promised by England's Industrial Revolution (which would precede America's by about one hundred years), one might imagine that some of his work could be pessimistic to begin with, but he started writing novels long before he began working with poetry.
There are exceptions. "The Darkling Thrush" is a poem full of hope. "I Said To Life" speaks of a loss of love in general. And there are other poems that do not fall into the category of "death." However...
...in 1870...Hardy met and fell in love with Emma Lavinia Gifford, whom he married...Although he later became estranged from his wife...her death had a traumatic effect on him...His Poems 1912–13 reflect upon her passing...preoccupied with his...wife's death, [he] tried to overcome his remorse by writing poetry.
And while not all of Hardy's poems are about his wife, Hardy wrote many other poems that were also about death. For example, "Drummer Hodge" was about a drummer who died and was buried in Africa during the the first of the two Boer Wars in which the British were involved.
Based upon the article from Wikipedia.com, Hardy started writing poems to help him cope with losing his wife (even though they were no longer together when she died). Because of Hardy's motivation for writing these poetry in the first place, it is safe to assume that he was preoccupied with loss and death.
Therefore, death is a common theme in Hardy's poems.
Death marks Hardy's poetry. It is viewed by Hardy as man's enemy together with Time and Chance who conspire to deny man and his existence of meaning.
Hardy however glorifies man's spirit by his personas' resilience and struggle.Man does not allow the cruel and insensitive world to kill his spirit.In so doing ,man defeats Death by securing his dignity .As is seen in "During the Wind and Rain",Hardy highlights man's tenaciousness in spite of his consciousness of the hostile environment.
Therefore, Hardy's treatment of Death is ironical. He offers hope in a seemingly hopeless world that has robbed us of our faith in God.Hardy's focus on Death teaches us how to live in the face of the inevitable and so, be triumphant against the foe.