Sure and it actually comes from Barbariccia and then later 2st boss of Rokkon (criterion), seen as bullet hell mechanics that they improved upon since then. We also see that kind of thing in Vanguard. In all cases there is different speeds and paces, and the width and shape of the AoEs vary, as well as the randomness (some are scripted like in barbariccia, some are fully baited like in here, vanguard and rokkon).

But I'd like them to go further than just this. For example taking M2S as a fight since we're on M2, the mechanic that allows the boss to build up hearts as soon as people fuck up in the Beats phases is actually a great soft enrage mechanic, and I could see that kind of things in midcore content.

But more than anything I think people are also just fed up of being regurgitated the same trial arena with a boss model over and over. They want more unique and creative things to crop up again like we have seen in the Bozja instances like CLL and Dalriada, and it's not exactly hard to retranslate this into duty finder content either.