Ran some tests myself, Centigrade, embarking with 3/3/1/1/1/1 Crossbow/Axe/Shield/Armor/Dodge/Discipline
Producing and then assigning leather shield, copper crossbow, bronze battle axe over clothes resulted in the axe being strapped to upper body and never used. Replaced crossbow and shields with wooden ones, since the combat log was kinda short, equipping everything at once...and the dwarf didn't shoot, with different wield order, due presumably picking things up in wrong order.
However, removed and added shield got it strapped to upper body, even in combat, and had the military dwarf always shoot, and most of the time hack with axe (there were some wooden lovetaps, though less than axe slashes). No shield blocks in 3 pages after that, but there were only 2 in 9 pages before, so that's not saying much.
Did the individual, sequential pickup again with leather/wood/bronze shield/crossbow/axe, with now changing to exact matches (always used specific shield/weapon/weapon)...And same initial result of not using axe once in 20 pages. By now, Hammerman was at 5, Crossbowman at 8, and axe still at 3, surely owing to the fact that being hacked in the head with a bronze axe kills training targets (still, quiverful of bolts sure lets dwarf catch animal sooner).
Remove leather shield and axe, then added bronze pick (with no mining skill) then leather shield in that order, waiting for pickup, since the thread mentioned axes in particular being preferred (and was in 31.25, I think?)...Eh, pick got used most of the time too.
Since I saw almost no retaliatory attacks by wildlife, put 3 training spears on repeat (42.06, so safe). No shield user experience, but....2,5k mining despite never batting a spear aside with pick? Slightly lower hammerman, I think.
Confirming that your dwarves are blocking, hacking and shooting?
Still, I suppose an edged weapon is improvement over shield in close combat for the marksdwarf. Melee combat, not sure how important a shield is, but against non-flying/non-AoE enemies I'm doubtful it is less important than shield.