Uhm did you play SHB and EW?
Both of the arguably hardest levelling dungeons in the expansion were Holminster and Zot.
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Not only were the EW and ShB first dungeons nasty, the first dungeon in HW, though optional, was not any nicer. Up to the first boss, Dusk Vigil is a warmup. But after you get past the mammoth you get to some gnarly bosses and mob packs that can be dangerous. The freeze dot from standing in the wrong place can quickly kill you and the flood of zombie mobs could gank you if you were not prepared with cooldowns, heals, and quick aggro management. I saw quite a few naive WHMs and ASTs get devoured by zombies when they cast a Medica 2 or a Diurnal Aspected Helios before they spawned. The second boss had nasty raidwides and potent adds back in the day, and the last boss could debilitate inattentive players.
Not sure what people are going on about in here about hard dungeons. The only hard dungeon in stormblood was the one in the steppes. Satasha was extremely rare to wipe in. In fact the only time I ever remember wiping in ARR leveling dungeons was if you got a scholar healer who didn't know how to play scholar yet. Tower of zot wasn't hard by any metric either so that one is especially surprising to hear.