I never said you should rule it out entirely, I am a big Opeth fan. But as Razoredge stated, it sounds, and often is very monotone. It has its place, but hell my favourite example is the band 'Marduk'. Its your stereotypical black metal band. Its just non stop in your face, including the screaming. Lyrics and vocals are my favorite part of music, followed by guitar being a guitar player myself. And black/death does not speak to me lyrically, and even if it did-I often don't understand the words that come out of there mouth. This is where I give Opeth much credit, because he can sound as soft as a snail, and as deadly as a panther, withing the same 2 minutes and I can understand what he is saying either way. I categorize it as cookie monster vocals not just because of the sound, but literally any kid can duplicate cookie monsters voice to a certain extent! All it shows in the individual is they have some fucking power, and props to them for being able to still talk and tour.