Check those out:Here's another growler whom I find not that difficult to understand - Johan Hegg from Amon Amarth:
http://www.youtube.com/watch?v=P3WJX1cIuY4
On first listen I understood the majority of the words.
Never heard these guys before, although I didn't mind it. Might check out some more of their music.
http://www.youtube.com/watch?v=lGINLisYN9Y
http://www.youtube.com/watch?v=O-2ltMoaav0
http://www.youtube.com/watch?v=0Ij5QOHEHSk