I wouldn't say they were disproportionate, certainly not after or before 1915. German casualties on the Western Front in 1914 were almost 800 000, and French losses were only slightly less. Add in Belgian and British casualties and both sides were fairly equal. Verdun cost the Germans 350 000 to France's 370 000, and casualties on the Somme were roughly 600 000 for the British and French, and 500 000 for the Germans. Casualties in the Arras Offensive were c. 160 000 for the British, c. 120-130 000 for the Germans, 244 000 for the British and at least 217 000 for the Germans during 3rd Ypres. Losses on both sides, German and Allied, were over a million in 1918.

The offensives of 1915 were disproportionate, in the case of the Second Artois Offensive the Germans suffered 75 000 casualties to almost 150 000 French. This was in large part due to Joffre's policy of remaining on the offensive, which was influenced both by political concerns (ending the war ASAP, liberating Belgium and Occupied France with their millions of civilians and valuable mines, factories and farmland) and the need to keep as much of the German Army tied up as possible, to prevent more reinforcement of the Eastern Front which was currently the site of the Gorlitz-Tarnow Offensive. There was also a military reasoning, in that German defences, while obviously strong, were not as deep as they would be by year's end and 1916. Thus, where there was success as initially there was at Loos and Second Artois, exploitation could roll up the frontlines nearby. Unfortunately, Allied firepower proved insufficient to force a successful break-in, and it would take time for the tactics already identified by Andre Lafargue and others in the French Army, to be disseminated and indoctrinated.

Attacking defensive positions was acknowledged as the most difficult task in war; even Clausewitz declared the tactical defensive was superior to the offensive. But despite heavy losses, Allied methods of attack vastly improved in 1916-17, and unfortunately, so did German methods of defense.