Compared to the number of times hogs are trapped or hunted, the number of issues with them is very small. It wouldn't surprise me to find out that there are more injuries from deer hunting than from hog hunting.
From the individuals I know who work with feral hogs for a living, the majority of issues come when the hog has nowhere else to go other than where you're standing. While I've never hunted them with an air rifle, I do have experience going after them with pistols and firearms. The closest shot I've taken was 20 ft with a 44 mag on a 300+ lbs hog on a hunting preserve. The boar was running towards me and then hit an open trail that ran towards a wood line and turned giving me a perfect broadside shot that dropped him in his tracks. Most of the time with baiting or open fields, the hog's scatter away from any odor or noise they don't like.
There's a company out of Georgia that kills thousands of feral pigs annually without having a single incident that I'm aware of.
