Someone who enables all the worst in others, egging them on, and keeping his own shoes clean is a very very realistic horror story.

Yes! Which really struck me on this reread, when I'd previously been paying attention to the melodramatic Gothic horrors and aesthetic stylings.

And it makes some of the melodrama snap into place more: oh, of course James Vane oh-so-conveniently gets shot by mistake, if the nature of Dorian's whole supernatural thing isn't just Eternal Youth/Spooky Portrait, it's that he's immune to consequences (except those he inflicts on himself). Damage bounces off him to land on everyone else around.