I think the issue here is not what kind of armor is being used, or if the throat is covered or whatever. The issue is putting near-green recruits into candy armor and candy weapons and expecting it to count as lightsaber+5 against the goblins. Goblin use crude weapons but they use them well, that's why they are goblins. Inexperienced dwarves should not be equipped in addy--not only because they will die almost as swiftly as normally, but because the ones that survive will lament and rage and maybe massacre the fort with said weapons, while ignoring hammerers with said armor.
1. Danger rooms are effective but cheap (aw man first winter already and only 7 out 10 soldiers are fully legendary, damn!)
2. Without danger rooms a military is something to cultivate and develops, avoid certain fights and attack from a certain angle in others-- a truly well-trained soldier can devastate whole sieges, but the same soldier shot and killed is difficult to replace. It is emphatically not the same attitude of "cannon fodder" most r.t.s games cultivate to an extent.
3. Adamantine is not a super metal, or a magic metal or an auto edge in combat--it's just really sharp and really light metal. To use blue weapons and armor dwarves need to know how to use the regular kind first, and worst, addy brings more goblins early, due to the value, and as mentioned above, makes temper tantrums into bloodbaths, again early on
4. always wear 3-4 shields