They were more than a novelty; the Windbusche at the time was a terrifying weapon system in the hands of trained soldiers. Their problems of fragility were easily countered by simply putting them in the hands of well-trained and drilled professional soldiers. Previously, in their earlier trials, they were placed in the hands of regular infantry whom had a tendency to mistreat them.
Unfortunately they did require master craftsmen to construct them, particularly the complicated systems of the air reservoir and valves/tolerances. The tanks did take a very long time to fill via handpumps, but it was military doctrine at the time to wheel a horse cart filled with a few hundred pre-filled reservoirs to quickly restock the troops, in addition to the one or two spare ones they carried on hand. I believe there was also a horse or water-powered system of pumping air into the reservoirs, given the immense amount of time required to do it by hand.