I would also support gating savage/extreme content behind a test where you can prove you are worthy. However the test should be more than just a passive striking dummy. It should have mechanics similar to the actual fight. Otherwise you're going to get players who pass the test but can't keep up their DPS when they need to dodge mechanics at the same time. Party finder should have an option to require players to have passed the trial, so that the party leader can set it as appropriate for practice, clear and farm parties.

Requiring a particular clear time in SSS or other similar way of requiring arbitrary player-supplied DPS, on the other hand, is elitism. It allows requiring much higher DPS than is actually necessary to beat the fight. If you want to save those precious seconds of your time, set up a static. That not only allows you to vet players based on their ability, but consistently playing with the same group will also allow you to work tighter together than a bunch of random people.