I considered them "magic-spawn" until seeing that trick with Wind Waker. They might possibly be a race, an enemy-race similar to Moblins. (I always considered Moblins a race in their own right - from the beginning, since some of them try to help you in the first game). Both races could be both, actually - originally magic-spawn, but creatures that developed a race of their own. I can imagine Darknuts as a Proud Warrior Race just because, man, they are powerful.
In the original/first Legend of Zelda game, my favorite way to combat the ROOMS FULL OF THE FREAKING THINGS is to be at full hearts and hang out in a doorway, shooting out at them/shooting out randomly until I hit them. Unfortunately, in that game, they move rather fast and can clip you when you're just outside the door. When this happens, I'll hide behind statues and try to clip them when the come by. Also, planting bombs and running away is a favorite technique.
I loved how in Twilight Princess they had two techniques - the heavy armor, then the graceful long sword.
They're interesting enemies, definitely. It would be nice to learn more about them. Then again, I'd love to learn about Moblin culture in a future game and I'd like Nintendo to bring back Lynels and expand upon them.