I had this whole post, but it went away when my backspace decided it meant "Back" rather than "delete the character to the left" so, yeah, not rewriting it all.
Mostly, I didn't mean that "Hero" compares to "Becoming Part II" or "The Gift" or "The Body" or "Chosen" or "You're Welcome" or "Not Fade Away" or even "Seeing Red" on plot. But most of these are not episodes that I associate entirely with the contained death, exactly. "You're Welcome," yes, and that's the only episode of these I'd say has close to the same tone. "The Body" isn't about Joyce at all, it's about the pain of losing somebody. "Seeing Red"s death is designed to anger you with the sheer randomness of it all, which is powerful, but not the same effect at all. The others are all season finales, with the associated amount of plot and climactic feel that, to some extent, ofter overpowers the deaths.
In fact, maybe that's why "Hero" works so well for me - because the plot, as you say, is kind of craptastic. The only memorable bits of the episode are Doyle. Doyle on camera. Doyle facing his own personal demons. Doyle finally getting Cordy's attention. Doyle realizing what he has to do. Doyle pushing Angel over the edge, jumping on the shiny ball thing, and exploding in a burst of light, fighting all the way. And finally, "Is that it? Am I done?" It's an absolutely wonderful swan song for this funny, normal guy, a generally reluctant hero who finally finds redemption he didn't even know he needed, in the eight episode of a series centered around redemption. His death wasn't expected, but it wasn't employed for shock value, and it feels truly earned. Without "Hero," would I really miss Doyle? I don't know. I don't think I really loved him until he was gone.