They're Kallistra models rather than Pendraken.
Artillery is a powerful tool in Square Bashing - each side has the chance to call for barrages throughout the game - with two different types available - suppression (which, as the name suggests makes firing and advancing tricky) or "point effect" which is more concentrated and devastating.
The point effect barrage that the Germans landed directly on the British defenders (aided by their airborne spotter) was so effective the British were thrown back, leaving the chateau undefended.
So yes, barrages can be effective and decisive but they are limited, have a chance of landing on your own men (or not coming at all) and ultimately you'll need to do some work at the point of a bayonet
It feels quite WW1 to us (if you're prepared to persist with quite a poorly laid out set of rules that is!)