The key is to get to know the actions of the mobs. You are going to need to roll a lot, Roll in to attack, R1 R1 (maybe a 3rd R1) if you can get away with it then roll right out and get ready to roll back into range and do it again. Don't forget to use L2 from time to time, I think I played half the game with Luds sword before I learned you could L2 an overhead 2hand chop which has a huge reach.
You have the option of hitting R3 (push down on right joystick) which will lock the target, some times this helped immensely, sometimes it killed me. While locked on target you jump back instead of roll away which can make it harder in some cases, try both and see what fits your style better.
The basic start I used for most hard stuff was to run at them, roll past them and get 3 good shots at their back, roll away and repeat as needed
The next boss you face, Father Gascoigne, was super hard for an early boss. I NEEDED to use the environment to keep space. Then used R2 charged attached to get the hard long hits.
DO NOT GET DISCURAGED, but be open to taking breaks.
