I did a quick look at Dyers but they don't tell us how many men were in each regiment.
I appreciate your efforts and concur that every battle had different factors to consider. Without data from each conflict to compare it is just an educated guess. One could make a point for various personal. Color Bearer , Officer atop a horse, Artillery crew, Submariner,Driver of a munition wagon, or just plain grunt, no one was safe from fire , disease or exposure.I did a quick look at Dyers but they don't tell us how many men were in each regiment.
For example the first Mass Regiment heavy Artillery which saw service most of the war lost 9 officers and 232 men in combat vs the 1st Mass Inf 8 officers and 176 men but we don't know the seize so we don't know the percent. The above figures exclude disease combat only. @JOHN42768 could indeed be right but since he made the assertion some hard data would be nice. Then we have to weigh the fact some regiments saw far more combat then others . Some battles were far worse on one branch then the other for example the battle of Nashville the Union artillery had less incoming shot vs the infantry which pursued Hood's infantry. A whole lot of variables.