Weapons that are effective against DLC bosses?

Just wanted to know if anybody has figured out what is really effective against the bosses in the DLC. The only thing I have found so far to be effective was Crystal Soul Spear and Soul Spear, along with other strong sorceries. That does not say much for weapons though.

I also would like to know what is effective against the Stone Guardians that roam the Royal Wood. Those things give me a heck of a time, especially when I am on my 5th play-through.

Haven't tested it, but I have a feeling that Artorias is weak against fire-based attacks.

And killing him with sorceries is easy as hell, really, 1 Soul Spear (at 44 int with Logan's Catalyst) took around 17% of his health. And you can have 2 Soul Spears in NG, so just spam those 8 Soul Spear (4 per copy), and he is down.

Kalameet I haven't tested anything to be honest. I just killed the darn thing.

Sanctuary Guardian, well I think he doesn't have a weakness.

Manus, well, sorceries worked pretty well against him.

Zwei buffed with Great Magic Weapon! I owned Arty with that!

Fire is so weak against him its not even funny. A fully upgraded and ascended glove with chaos fireball did around 100 to him. I just do PW and doublehand my +5 Abyss Greatsword. He goes down hard.

Great Scythe works well for anything and everything. Manus, Kalameet, and Artorias are all jokes when it is used properly.