The thing about magic formations is that while they look sophisticated, their principle is actually very similar to a circuit board. They are channels for energy transmission, the only difference being that one guides electric current and the other guides magical power. Setting up a magic formation is not easy.
The slightest mistake requires a complete restart; there can be no carelessness. But destroying one is very simple. As long as a small part is damaged, causing an excessive accumulation of energy, the formation will basically lose its function, and this excess energy will ultimately be released in the form of an explosion.
Hill's troops split up to act. They did not care in the least whether they could injure the mages maintaining the formations. The moment they found a formation, they would toss a row of alchemical bombs at it, and then, without a second glance, rush toward the next target.