Actually, my method is to stock all three life rings and do the clears. In this way, you basically have infinite attempts and if you eventually clear the hall, you have a nice stash of souls to use to replenish stocks with. The hallway in that instance was actually fine, because all of the shit you take on are just junior versions of him in open terrain. Compared to the Smelter Clear, it was a joke. He also was not that difficult of a boss, at least not with a stock PVE mele/miracle/curse setup. Once you get his moves down, the classic roll and counter does him in. Smelter 2.0 was an utter fuckover, though. Finally gibbed him by gearing up to spam curses and just dashed to him with two NPCs. I let them tank him while I spammed Curse based poison and Dark Balls at him. He is utterly stupid to try and solo or mele, though.
Of all the bosses in the DLC, I think Fume Knight and the axe curse bitch from the first one were the hardest. Both had odd unpredictable moves and required gearing in a specific way to handle the attacks. Both had random elements to them I did not care for. For example, if Dark Bitch summoned skeletons twice, it is easy mode victory, but if she spawned the bronze buttfucker twice, it becomes a much harder fight. I also think the smelter fight was largely a copout and I would have preferred something new or less build restrictive, like Gargoyle 2.0 or something Gaping Dragon-esque. Overall, though, the DLCs were a lot of fun, though not very co-op friendly for those of us who want to go back and help others out. Right now I have everything cleaned out, short of the Dark cult stuff (no point with my build burning all of those effigies) but I am shelving this until the third one comes out.