So I finally decided to get around to playing the Zelda DLC but I am stuck on the opening of the Champion's Ballad. I am struggling to clear the camps in the Great Plateau with the One Hit Obliterator. Any tips on how to get past this part would be greatly appreciated.

Yea that part kind of sucks, especially since it gates you off of the rest of the dlc. I don't have many tips besides some that may seem obvious, as far as I know there isn't any way to really cheese it. The challenge doesn't limit your use of your bows and arrows, so try using stealth as much as possible with the Sheikah Armor or food. Also you can use the Bokoblin/Lizalfos/Moblin Masks or Majora's Mask to lure and isolate enemies, or trick the enemies into not attacking you until you attack them. You can also use Statis+ to lock someone down who engages with you or to identify threats since the yellow filter makes it easier to see enemies in the darkness I find. Abuse manual saves too - as soon as you take someone out, make a hard save and just save scum it if you make a mistake. Good luck.

Aside from the above, combine lynel bows with bomb arrows and ancient arrows to carpet bomb the shit out of any large enemy settlements. You might also find a phrenic bow useful, which you can consult various wikis for locations of if you don't have one.

I actually liked this part of the DLC. Got to combine the decadent fruits of hundreds of hours of play with whatever cheeky tactics I thought up on the fly, and for once in well over a hundred hours of play I actually felt vulnerable.

Don't rely on the sword too much. I took almost everything out with arrow and bombs. When something does get up close remain as defensive as possible and then hit them right after they attack. I typically lured enemies away from the camps one by one.