But his EIC rule was also when Frank Miller, Walt Simonson, JB and Bill Sienkewicz (!) exploded in popularity and they were obviously the opposite of subdued or boring.

Maybe the numbers they brought in made them untouchable to Shooter? Did he encourage them or barely tolerated them? From some of the accounts (including JB's) it sounds more like the latter.

He was at a panel a couple of years back, and talked about how Miller brought a cinematic / storyboard quality to his work.