I found he was overrate but still a good character overall. By the end of the game he was doing much less damage than Yuna's spells and Tidus' attacks, and his overall stats were worse except the hp on my file. I also have come to the conclusion that his character had a commonly overlooked darkside to him.

(SPOILER)He used Tidus and Yuna at different points for his own personal gain in order to get to Yunalesca, who he blamed for Jecht and Braska's deaths. She had also killed him when he returned after the final summoning Braska had conducted. I think Auron wanted revenge on Yunalesca a little more than he cared for killing Sin once and for all...