They have plenty of counters, even nondoctrinally. They have flamethrowers and flame ht if the bofors braces, they have mortars (the best counter) they have paks of the pit is occupied or braced, and later on they have the brummbar and pwerfer, which absolutely wreck sim cities. Doctrinally, they've got the mortar ht, the puma, lefh later on (another sterling counter), and the elefant, as well as offmaps. Or you could always just force a brace on the bofors and rush in with a bunch of grenadiers and maybe a flamethrower. That works too.
All these non doctrinal "counters" don´t work if the cancer pit is placed behind a shot blocker. And even if you reach emplacements with flame weapons, a Bofors will kill off any infantry or flame HT faster than the other way around. Usually the Bofors will survife the flames while braced and then the funny situation occurs that the Bofors unbraces and finishes off the supposed hard counters within seconds. Moving Paks into mortar pit range also means dead Paks. The same goes for regular mortars.
Long story short: Ostheer has no cost effective non-doctrinal counter to emplacements. The micro burden is on the Ostheer players side. While the Brit presses one button, the Ostheer player must apply constant pressure with units that are fragile to the emplacements. If the Brit manages to stall the attack the manpower bleed will cripple the Ostheer player while the Brit just needs to repair.