As was pointed out earlier, the MSQ isn't there to prepare someone for raids. It's there to prepare them for the next stage of the MSQ.
It doesn't matter how hard SE makes the MSQ, those players will never be prepared for the difficulty of the optional content. But making it difficult will discourage them from continuing to pay for the game and help fund that optional difficult content you do want.
If you end up with someone in the group that can't handle things, then remove them from the group. Be polite about instead of being a jerk but remove them.
And yet it's SE that sets the difficulty level for the MSQ content. The question becomes if that difficulty level is reasonable when it is their game design funneling players of all skill through it together.
Getting players invested in a story then telling they they can't continue with the story because they've hit their personal skill cap or comfort level for difficulty is a pretty crappy way to design a game that survives on subscription retention. All you do is turn away people who were otherwise happy to support the game financially.
Why I wish damage meters were a base part of a game UI. People need to have an objective measure so they'll know if they need to improve to enter into certain content. They can then choose to work to improve or accept that more difficult content is not right for them. Most people will understand they're holding a group back when presented with an objective measure of their performance.
It doesn't change that I don't feel that the MSQ is the appropriate place for skill tests to be implemented since it's mandatory for all character progression, even for players only interested in crafting and gathering.
The skill tests should come with the first encounter of the optional content. If you can't defeat the first, then you can't continue to the second and so on. Another option would be to expand Stone, Sky, Sea and The Circles of Answering into scored proving grounds. If the player fails to perform to a set standard there, they can't queue for the related duty. Groups created through Party Finder instead of Duty Finder are always free to remove a player at any time. You just can't be a jerk about doing it.