Nick from HireArt here. I definitely agree with you that video interviews tend to be very time-consuming. One of the services we offer to employers is the grading of the interviews. We also keep the video portion very short (~2 1-minute clips per interview).
I'm the tech co-founder on our team. I do all of the development for our web app.
The grading is not automatable, but I suspect it's scalable. We're finding lots of quite talented people willing to work part-time as graders, and we streamline their grading process as much as possible. We also try to provide very very rigorous rubrics and use multiple graders for the same interview to ensure standardization of the grades.
How do you qualify the graders? Is it on a case-by-case basis, reviewing their resumes & speaking with them? I could imagine that aspect of the process requiring some creativity to scale without losing quality.
We've been bootstrapping the process by using our own app to hire graders. We administer work sample interviews on our site (i.e. we give the applicants dummy interview responses to evaluate) and use our current graders to evaluate them.
I'm the tech co-founder on our team. I do all of the development for our web app.