use a little common sense here.
War fought with Guns -
People hide in holes and shoot at each other. People die, but also anyone has a chance of living.
War fought with swords -
People run at each other and start hacking with swords. Once someone dies, the person that was fighting that person will go look for someone else to fight.
In "modern" wars (anything since the US civil war) We would be completely agast if casualties reached even 10 percent.
In ancient warfare it wouldn't be surprising for the winning army to have casualties approaching 30%. Losing armies could be close to completely wiped out.
The difference? In the ancient method the only way for you to survive was for you to kill. In modern warfare you have the option of killing or hiding with hiding being the more effective of the 2.
Of course ancient war was more bloody. And we really wouldn't have much choice in how we fought our wars if the technology level were returned to that level.