My experience with Campaign Series is that once an AT gun or artillery piece is spotted unless quickly moved that unit's life span is very short.
Last turn my forces spotted a small howitzer battery located on my side of the Our River. I needed to keep in mind op fire for American tanks coming out of the woods but I hit that battery with some MG gun fire, at least three platoons of Panzers, even a shot from a Panther, AA guns, etc, etc. I think last turn I could only get a 1 SP loss and disruption.
This turn I threw the kitchen sink at this unit (the sink being that 88 and 75mm AT gun 750 meters east) and was starting to get worried about having to use my Panthers to eliminate the unit. I was really worried about that unit continuing to direct artillery fire. Fortunately the position was eliminated along with the assorted trucks and half tracks scattered in the woods.
I had to make a screen shot in honor of the brave American gunners.
The American infantry unit was forced to retreat. A M-10 platoon engaged and destroyed a PZ-IV but op fire from a Panther destroyed two M-10s. They also retreated into the woods.