You mean the bed of chaos...that one was a hard one. To me there are worse boss fights but that is because once you kill one of the sources holding up her barrier they stay dead. I was able to beat by using light armor, for increased speed, my black knight's halberd, because it is my favored weapon, and then at the last moment when the floor falls from underneath my feet i rolled onto a tree root. That tree root is where you need to land in order to get a chance in order to finish off the boss. There is a pattern to how the floor collaspes, and you have to have patience in order to notice it. That is the key rule to beating dark souls, you need patience.