I sort of suspected this back in Demon's Souls, where it seemed like a lot of the bosses' dead zones seemed awfully prominent. The Leechmonger had an obvious plank jutting out right at the entrance where he couldn't hit you, the Spider had all those alcoves where he couldn't reach you, the Maneater was clearly visible through the fog door, and the boss fight was built to compensate for the possibility that one of them was dead before the fight even properly started. At first I thought these were all oversights, but when From patched the bosses who were vulnerable to Poison and Plague so that they were immune to Plague but could still be Poisoned I started to doubt that. They clearly knew the bosses could be safely cheesed to death with damage over time, and instead of making them immune to both they only made them immune to the faster option, leaving the slow, grindy option available. It was like they were saying "Yeah, you can cheese 'em to death, but we're not going to let you do it fast."
That's when I started thinking that some of them weren't so much oversights as they were intentional cowardly options for folks who couldn't hack it. The closest thing to player-friendliness From was willing to engage in, if you will.
I might be giving them too much credit, but some of the bosses in Dark Souls bolster the hypothesis, I think.