I tried to separate on-screen presence in my original comment, but her kayfabe actions and backstage role are probably too tied up for this.
As far as castrating faces (and heels) goes, yes, true, but Shane since basically the beginning would always go toe to toe with the top stars and, depending on whether he was a face or heel, often get the better of them. I remember Rock selling for him to a ridiculous extent, in 2000, when Rock was bigger than wrestling. Sure, Rock was always really selfless for a top guy, but he was not the only one. The only one who treated him like a proper jobber was Steve Austin.