Well I haven't fought the 4th time but I just fought the 3rd time and thought it was a pretty tough fight! It was only the second time playing the game so far that I'd had a game over..it was that total annihilation thing that did it

The second time I tried though I just kept using Holy and finished him off with Bahamut's overdrive, was lucky because when he did total annihiliation he KOed two characters and left Auron with 600hp ..it was close

I'm relieved to hear that the fourth fight may not be so bad