Well, I'd say the "ideal" form was and is the combination of "stosstruppen" infantry tactics with the shock/speed of armor -- but in general I think Watchman has this nailed down pretty well.

Also recall that the front's involved, particularly in Flanders and the Argonne, were a nearly continuous system of defenses. No flank, no options.

The BEF of 1914 was the era's best army in the world, man-for-man. At Mons canal, facing BEF riflemen in scrapes, the Germans thought they were facing machine guns! The only other troops recorded as having shot well and rapidly enough to create this effect were the USMC and all they could deploy was a heavy brigade.

Kitchener was incensed that the BEF was almost fully deployed, however, because he knew the casualties would be high and that he could never replace the experience lost by the "old sweat" regiments -- which he valued more as the cadre for his million-man army than as an independent fighting force. The losses suffered by the "Pals" on the Somme may well prove him correct.