I'll just point at that before the 2h update and some changes to how pDIF and level correction worked, those were the only things making XI difficult.

You had a game where the "boss" mobs took -50% damage from a Lv75 character from the get-go, not accounting for the fact that players could not cap pDIF (making that -50% more like -80%) or Accuracy. This is why Ranger and Black Mage were the preferred end game classes. Black Mage has an easier time dealing with higher level mobs, and their gear is easier to stack for such and Ranger suffered almost no level correction penalty.

"Difficult" should not be confused with "poorly designed". You're talking about Dynamis Lord kills in a period of time where 8months earlier WAR was tanking things by spamming barspells and PLD was a main healer.