I do think that the difficulty should be slightly increased, but I'd say more towards late-ARR and HW and only if the game teaches players better. The first boss of Dead Ends, for example, has a high body count less because the fight itself is hard, and more because a lot of first-timer healers never truly needed to esuna stuff before.

I'm also of the opinion that content being too easy also removes some of the MSQ's luster. Thordan's fight makes base HW's ending feel flaccid, and the Cape Westwind trial/ the old MSQ roulette (all of them now defuct, thank god) REALLY didn't do ARR's finale any favors. Here's hoping Square gives the same love to Thordan as they gave to Rhitahtyn