I've beaten him, but I can't quite remember my exact strategy for doing it... let's see...
1. I know that, by then, I had the Ultima Weapon. This made things 10x easier. Plus, I think I was only level 80, which is pretty high I suppose, since most people can do it at a much lower level.
2. Use Reflega to knock back his orbs; or, you could just hit them. I think I ended up just hitting them away.
3. It's a good thing to already have Glide, or at least Quick Run. This way, you can quickly escape him when he begins summoning the eruptions around him that tend to suck you in.
4. Berserk Charge is controversial. Many people say don't use it, because if you use it too much, you won't be able to combo him at the end. Personally, I found it to be extremely helpful, and I just used a Horizontal Slash at the end. But really, it's to each his own.