Main Scenario Restriction Bloodstorm - Very Very Bad idea.

[Reynhart]

Even at release, Ravana was easy.

Not for everyone, and there was legitimate tricky mechanics than can surprise you even if you're a good player.

People who cannot be bothered to learn their jobs, won't stay.

That's where you're wrong...they stay...and they complain over and over about how <insert_instance_name> is too hard.
Besides, job is not the only thing that the MSQ teach you. You also face a lot of important mechanics in those fights.
The gaze mechanics, the pack mechanic, the break-the-chain mechanics, the tower mechanic, etc...all of those are taught in a "newbie-friendly" way in story dungeons/trials so that you can deal with theirmuch harsher version in optional content.

[Bourne_Endeavor]

Not for everyone, and there was legitimate tricky mechanics than can surprise you even if you're a good player.

Right. And not everyone who used a jump potion would find him difficult.

That's where you're wrong...they stay...and they complain over and over about how <insert_instance_name> is too hard.
Besides, job is not the only thing that the MSQ teach you. You also face a lot of important mechanics in those fights.
The gaze mechanics, the pack mechanic, the break-the-chain mechanics, the tower mechanic, etc...all of those are taught in a "newbie-friendly" way in story dungeons/trials so that you can deal with theirmuch harsher version in optional content.

Are we really going to suggest these mechanics are difficult to learn? Gaze, you look away. Towers, one person stand in the glowy spot on the floor. Giant arrows targeting one person, everyone stacks. All of these can be figured out either through very simple trial and error or by being told exactly in the manner I just did. Not to mention, plenty of people who may favor a jump potion are already MMO players and would have a general idea of those mechanics, especially trash pulls. Furthermore, a "Proven Grounds" like how WoW does it, would explicitly showcase these mechanics if you were required to complete certain dungeons. That all said, you can learn how to play this game within a day using nothing but Youtube. When I first started tanking, I looked up newbie tank guides, then those dedicated to Dark Knight. Those taught me far more than the game itself ever did. Keep in mind, people like MrHappy and Mizzteq literally explain every single mechanic you'll see in every dungeon within the first week of their release. Someone skipping ahead may also have friends, who would explain mechanics and/or the selected job.

[Reynhart]

Are we really going to suggest these mechanics are difficult to learn? Gaze, you look away. Towers, one person stand in the glowy spot on the floor. Giant arrows targeting one person, everyone stacks.

Considering they had to nerf Blighted Bouquet because "Stopping any action" was apparently really difficult...yes, we might suggest that

But the problem is not the difficulty, but the punishment. In dungeons, failing these mechanics won't result in a wipe, so you'll have time to learn how to deal with it by yourself.
In raids you fail a stack, you wipe, you fail a gaze, you wipe, you fail a tower, you wipe, you fail a split, you wipe...

[Bourne_Endeavor]

Considering they had to nerf Blighted Bouquet because "Stopping any action" was apparently really difficult...yes, we might suggest that

But the problem is not the difficulty, but the punishment. In dungeons, failing these mechanics won't result in a wipe, so you'll have time to learn how to deal with it by yourself.
In raids you fail a stack, you wipe, you fail a gaze, you wipe, you fail a tower, you wipe, you fail a split, you wipe...

Touche.

Yes, but they wouldn't be going into raids. If you were jumped ahead to Stormblood, it would be the equivalent of Heavensward now. So you would be doing dungeons and occasional easy mode primals. And like I said, guides are available as would be a "Proven Grounds" type requirement.