FFXIV's method of making things challenging is basically to give you a ton of buttons to press, and make you press them in the right order (rotation) while not getting hit by telegraphs. Nowadays most games have moved away from filling multiple hotbars with skills. FFXIV 2 or FFXVII or whatever would probably take a more modern approach instead of taking inspiration from early WoW.

That being said, tanking and healing is easier on the button combos than dps. Tanks usually have a damage combo + buff/dot combo + an aoe combo + some form of gimmick (IR fell cleave spam etc) + a bunch of cooldowns. It's easier than it sounds.