Our Heroes: Irish Officers Died In The Great War, 1914-1919

Findmypast has added a digitized version, indexed with 1,012 names, of the 1916 publication:

Our heroes. Containing the photographs with biographical notes of officers of Irish regiments and of Irish officers of British regiments who have fallen in action, or who have been mentioned for distinguished conduct from August, 1914, to July, 1916. Together with a brief military history of the chief events of the war in which Irish regiments were engaged. Vol. 1, Aug. 1914 - July, 1916.

An alternative source with additional information, including photos not in the Findmypast version, is http://ourheroes.southdublinlibraries.ie/ourheroes/.