Thanks for reminding us of this truly amazing poem. My thoughts went immediately to Matthew Arnold, "Dover Beach" -- I thought at first it was because I felt a similarity in the sentiments of the two poems, a sense of dreadful limnality (I feel less convinced of the positive or hopeful nature of the end of the Hardy poem, maybe because I just find it hard to believe that Hardy ever was any kind of an optimist). But actually even though my conscious mind can't keep one single line of poetry in it, I must have somewhere unbeknownst remembered the use of the word "darkling" which draws a great line from Keats through Arnold to Hardy.
And we are here as on a darkling plainSwept with confused alarms of struggle and flight,Where ignorant armies clash by night. It's pretty awesome (in the literal sense of that word) to read "Ode to a Nightingale," "Dover Beach" and "The Darkling Thrush" all in a row. Really a history of one very important strand of 19th century poetry, sending us headlong into modernism.