Eric/NNL knows his stuff and runs a great blog - huge fan btw!
That said, I have a couple of section 8 properties that I don't consider "D class" - I rent to section 8 because the rents are higher and generally lower maintenance. I would live in this neighborhood, no issues.
But if you can drop from 2% to 1.8% and upgrade from a C to a B, I would do it. Also, if you're managing it yourself and are hands on (as Eric/NNL is), then go for it.
I manage from 9,000 miles away so I go after C to B- properties, the smaller, older single family properties in good neighborhoods and school districts, as that is what works for me. My properties are in the 1.5% to 2%+ range.
I rent under-market and screen carefully - knock on wood, good so far and I'm continuing to scale up. That said, the 2% rule in my area (good neighborhoods, good schools but smaller, older homes) is rapidly becoming a 1.5% rule.