The important thing to realize here is that as judges we absolutely strive for consistency, but the context changes with each and every challenge, thus subtly altering the debate. We don't say to ourselves, "Aha, Selves! The rule is that leaving a dish off means automatic disqualification!" We say, "In this case, leaving the dish off overshadowed the other factors." In an episode of Season One we argued whether it was worse to leave off a major part of a dish or serve something so bad it was practically inedible. In that particular case, inedible was worse.
This never comes up when there's a clear winner or clear loser to a challenge. It's when the results are close that other factors come into play - two dishes are neck to neck, so we ask ourselves who stepped up? Who played it safe? Who forgot something, vs. who forged forward with a bad dish? It is simply impossible for us to cleave to some strictly defined criteria when the context shifts - sometimes in subtle ways - from challenge to challenge. Did we discuss that Tre had stepping up and taken leadership? You bet we did. But in the same breath we all had to agree, he f**ked it up. The food he served was terrible. We didn't send him home for sticking his neck out, we sent him home for doing a bad job.