First boss I killed on first try without any help. Used a +6(or maybe 5?) Dark Sword two handed, and all 10 Estus +6. Just roll under his hammer and hack away at his legs and tail. It should be pretty easy to get behind him. Every now and then you have to eat his AoE attacks but that's why you use the Estus.
Almost died right at the very end when he exploded. Then he took a knee and basically waited for me to finish him off. Kinda sad actually... never seen a boss admit their defeat like this before.