Scary part is, Soldier saint is wrong. That's how wars were fought. Nationalism to risk your life to defend your country was brought from propaganda, education system. When you can't instill nationalism to your citizens, they just leave the country when war happen, like Ukraine right now.
Is it plausible to apply these ideas here? I don't know if the story changed what it established at the start but iirc there are only small pockets of humans resisting here and there, the rest are either dead or enslaved by dragons.
So it's not like you can run somewhere else when, as far as you know, you're the last standing bastion of humanity where you live.
Also, if the number of people is limited, meatgrinder tactics are not really the best:
- Is the only way to make Third Grade guys by almost killing Fourth Grade guys? If so, isn't it better to do so in a controlled environment instead of throwing them into real combat situations?
- If you can create Third Grade guys with tactics other than beating people to a pulp, then It's better to train people who are more apt to combat and focus your attention to these more talented individuals. Make the less talented ones work in other necessary areas like logistics.
Maybe you can even try and develop some kind of way to use them (4th Graders) in combat with armament that require less training and are safer than melee. Firearms do exist in this world, but even if people don't know how to reliably make them, why is no one using bows, crossbows and cannons? There are a lot of weapons in history that where effective and easy to learn, way easier than swords... Almost everything is easier to train someone to use than a sword.
I understand that projectile weapons are probably useless against the raid-boss level dragons, but in numbers, they probably would take down smaller and mid-sized dragons.