Just attempted it with my first character, Sorcerer start with 26 INT. I had no idea how to dodge most of his fire attacks so I spent most of my time camping the stairs and waiting for the fire effect to go away, and popping off a single soul arrow at a time. I missed with a few, but the best part was my 30th soul arrow was the one that killed. If I had missed, I would have been screwed. I didn't even have a plan, I was just praying and got lucky.
I watched some videos on people using melee to kill it and I saw them exploit a small section on the edge of the bridge that was safe from his breath. It turns out that specific spot is colored differently, and I've heard that the game has been patched to prevent certain types of exploitation, so it begs the question. Is that invulnerable spot working as intended, or a complete oversight?
Also, I think I noticed something with the unit detection against the Taurus Demon. He performed a swipe in front of himself and I was spazzing out with rolls praying not to get 1 shot again, and though it looked like it went through me, it completely whiffed. Does the dodge have invulnerability frames, or do some attacks have grounded only hit properties, or what? I'm loving this game, but I want to learn what I'm doing wrong and what I'm doing right, and sometimes I just don't understand. The whole die over and over, then learn dogma is what attracted me to this game in the first place.