So what is so great about Auron

[ReloadPsi]

In a word: Meatshield.

In three words: Cool, badass meatshield.

As soon as Auron learns Sentinel, several of the fights become much easier. His Celestial Weapon is even designed with meatshielding in mind: It has First Strike and Counter Attack on it, meaning that even in an ambush, he can just use Sentinel and nobody gets hurt because his HP and Defense are so high. The Masamune gets stronger the more HP he loses, so his poor Evasion finally becomes his saving grace, making him even stronger. Also, because of all that, there's a good chance he'll murder everything before your other party members get a turn, obviously saving you some time and potentially some MP (but, if you play the way I do, this can be a little frustrating).

But that's only once you power the damned Masamune up. Until then, he's just a meatshield. Armour and Mental Break come in handy too, but you only normally need to use those once each per battle, if at all; after that it's back to using Guard/Sentinel while Yuna casts Protect on him for extra awesomeness.