I marched bottom bass and contra. The bottombasses have it the hardest. Insane drill, and very limited vision--more limited than contra--is hard enough, but with all that weight strapped on, just makes it worse.
Contras with limited vision to the left, and endless measures of rest are second with euphs and baris at a close 3rd. Just holdin' those puppies will do a toll on the guns.
As for high brass/ guard: Running just sucks. So they get 4th.
DM's don't have to jazz run at 3 to 5's and play at FFF...so no pity to them.
As far as the pitsters go, their jobs are just as hard, but at a different time.