Congrats on the victories.
And yes, Kalameet is the hardest fight in the DLC by a landslide.
Thanks! I can not say that he is also the hardest boss in the whole game outside O&S, for I just did this:
Ony used one estus. Finally defeated him on my eight try when I decided to go a bit more slow, and only hit him after either his four-hit combo, or his attempted grab-move. That way, it took some time, but it was safe and quite easy to get him down. Used the Greatshield of Artorias for high stability, Mask of the Child and Ring of Cloranthy for Stamina-regen. Awesome game, 10/10, would beat again!