Isn't it better to just make the lower level rotations better? Like, introduce the core of their endgame kits as older buttons that were removed before? MNK is a good example of this.

I said it before, but just imagine a lvl 90 SMN dropping giant primals on level 15 Sastasha bats... Of course, a sprout's first reaction is going to be "woah that looks cool" but then it'll get old pretty fast. This is a game that boasts its story telling, so I think immersion is a big part of it too... You can say "well glamours are immersion breaking" but I think a Roe in a santa outfit is less harmful to a sprout's first experience than extremely flashy moves that do no damage to a bum pirate.

Not to mention, how exactly would you balance healer and tank kits in old content? I haven't seen an answer to this yet.