See the people in this video he attacks? He kills them in 7 seconds or less, which is how classic works. It may not be how it works in your mind, but that’s how it works in reality.
People in classic have 4k health. Evisc/cold blood hits for 3ks.
I’ve been playing the game since vanilla. And I remember exactly when people stopped being killable. It was when TBC came out, and introduced resilience gear. Ever since then players in the game have become immortal.