Prelude seems like a way to just get more regular orbs at this point, since it's nearly useless for learning the fights, so I do feel like it should have separate weeklies. Well, I think you could use it to learn the fight if you have a dedicated group that wants to learn it together and is starting off by seeing the whole fight/practice positioning without wiping, but with pubs it's not going to be the case. Since little will kill you, nobody really tries to bait or engage with the mechanics much. You have to have a group that's opting in to at least trying that if you really want to learn much from it. Like when I was helping people in my alliance learn Mercury, it probably would have been a better idea to switch to Prelude because people were kinda afraid of getting in close and it would have allowed them to learn how to attack safely with more room for error. (...we never actually cleared together, I guess, but I think most of them have gone on to do so separately thanks to Expert being a thing. Though not always as their original characters, hmm.)
And yeah, I feel weird about Standard now too. It's kind of a weird gate, because it makes total sense to move on to Expert ASAP - especially for, say, Mercury or Zodiark - but that makes it even harder for other people to break through it to get access to Expert. There's no incentive to keep running it beyond the lower difficulty, since the drops are that much better on Expert even if we're just talking about orbs, but most of them still aren't pushovers so it's not that much of an appeal for me. And then you also have people (...like me, a few weeks ago) who really do jump right to Expert after 1 clear. I at least made an effort to learn separately from running, but it can be frustrating to see people clearly not know what they're doing when the requirements are much tighter. But I know I've benefited a lot from there being no additional gate, whether that'd be imposed by game or a way to tell how many times people have cleared, so... it's not like I can suggest that would be good to add. As a result, I've been trying to remember to switch my title to the relevant TA one to give people some confidence in me, but it can be hard to remember to do that (though I have it on my best one by default, which hopefully helps still).