I think you're right that especially for brusier champions damage reduction is superior gold for gold vs damage. I think by also choosing team comps without a "dedicated tank" the sunfire cape + defense items are also a product of necessity. In my experience bruisers damage scales fairly well off abilities or passives, (Jarvan passive, Irelia true damage, Nasus Q, Jax Ult passive,W etc) so the need for high damage items isn't there, when combined with how they deliver damage; up close and personal the need for damage mitigation is obvious. I suppose i'm not telling you anything OP you don't already know but I thought I would weigh in and add my support.
P.S Ad hominem attacks against the OP do not make his arguement invalid.