I feel Warrior is the lightest on the number of abilities compared to the other tanks, with about 32 buttons, not including extras like potions.

With an MMO mouse with 12 extra buttons, I'm able to map almost all of my abilities when using keys 1-6, Q, E, and Shift as a modifier.

One thing I like to do when learning a new job is put all my abilities on my hotbar right away, since the game does show you everything you will learn up to level 90. It gets me used to what I'll be pressing and I can adjust things later.