I totally agree about the quality of his growls, starting with the Royal albert hall dvd and culminating with the latest Bloodbath dvd.
But Mikael actually cleared this up in a recent video interview. He said that the reason his growls were bad was that he started using in ear monitors, and they made him growl with a different (bad) technique, due to how he heard himself in the in ears. He switched back to regular ear plugs, and he didn't have the problem anymore. And if you watch recent live videos, the growls are alot better than they were a while back.
You're my hero of the day!