Ex6's solution still works as of today!
Here's the link again: https://www.ex6.eu/2017/09/warframe-how-to-solo-no-brainer.h...
ALL CREDIT FOR THE SOLUTION GOES TO Ex6, this is NOT MY solution.
I just wanted to add a tipp to make it even easier:
Take Ivara and use her Noise Arrows to lure enemies into the lasers, which Oxomoco has lots of since it's located in the Void. That being said, you'll want the biggest range you can put on, to alert as many enemies as you can at once. Also, a large energy pool helps.
Laser kills will count towards your level completion, but will not mess up your headshot counter.