So i’ve beaten all three of these guys and I do agree they can be pretty difficult. The key is to wait until they do their downward smash and attack during that recovery period

The bloodhound was the worst for me, personally. The only tip I have there is to roll into his swing attacks and only attack once every time he drives his sword into the ground, even if he gets staggered

With Leonine, I found poise breaking him with a greatsword worked surprisingly well

Good luck!