I finally beat Ornstein and Smough, with the help of a blue phantom. If you're readying this, thanks.
That fight kind of sucks, IMO. Not that it's hard, which it is, but it seems to have a gear check component. The guides all say Ornstein is weak to fire. Don't have fire weapons? Good fucking luck.
My lightning spear +2 was hitting for about 50. 50! Per the wiki he has almost 3k HP. That's 60 hits on giant beast with huge range and a move that's damn near instant kill unless you have lots of HP.
The second phase of that fight was very frustrating to solo. But with the blue phantom, it was cake. He was using some sort of fire spell that took off a fifth of Ornstein's HP with each hit.
I'm bad at this game, but I do feel like it's kind of shitty for this boss to be a big swinging dick unless the player happened to choose fire as one of their main damage dealing methods.