D by definition meets the FFmpeg's criteria because it's also a C compiler. Because of that I never wondered how D performs in the benchmarks, as I know for sure that it can give me the performance of C where I need it.
But D is not included in the benchmarks game at debian.net, which isn't fair to D either as far as I can tell.
https://dlang.org/spec/interfaceToC.html
Dunno about the Debian benchmarks game or their build environment. I did my own benchmarks and it was quite easy to write working D code compared to C, C++ or Rust. I used LDC, the LLVM D compliler as opposed to DMD. Dub is not that seamless compared to Cargo but given that you have to set things up manually, it doesn't encourage dependency hell.
If you're writing networking code, Go is probably a better choice than vibe.d.