I love the Gatekeeper, but it doesn't really seem to have served the purpose of preparing people for NM dungeons--nearly all nightmare shouts continue to have absurd AR/HR requirements that are way, way above what you need, because clearing Gatekeeper apparently isn't enough of a barrier to ensure #gitgud quality.
That said, I still think S3 should be a requirement for unlocking the queue option for content. If you can at least clear the DPS check, you should be 90% of the way there, and most players simply can't.