Think about it, other classes watch their resources and cooldowns, maybe not mana as much, but they usually have more to their rotation. Arcane is AB or AB+AM depending on the current phase of your DPS.
Not counting utility and Cooldowns.
Subtlety Rogue:
The main abilities used by a Subtlety Rogue ~ Ambush, Hemorrhage, Backstab, Slice and Dice, Eviscerate, Rupture(Refreshed by Evisc) and Recuperate.
Arcane Mage:
The main abilities used by an Arcane Mages ~ Arcane Blast, Arcane Missiles and Arcane Barrage if on the move.
So really, Arcane Mages DO have less to do than other classes, but that doesn't mean managing mana is less effort.