Little late to respond to this but, 2 people I thought Eyeless missed with his recent article about HMGs:

Peter Tagtgren - Vocalist/guitarist/producer. His efforts in Hypocrisy, Pain, War, and The Abyss not withstanding, his work as a producer at his Abyss Studios had a major impact on the more melodic black metal bands back in the late 90s-early 2000.

Burton C. Bell - Fear Factory vocalist. May not have invented the harsh/sung vocal concept but certainly the one to really make an impact with it with Soul of a New Machine in 1992. Pretty much set the template that thousands of bands have followed since.

I could probably think of some more but none come to mind at the moment.