Yeah even I had to go out and around to find every little bit of upgrade and advantage I couls find to beat him in a str meele build.
Find the 4(?) golden seeds around limgrave, use the NPC summon, upgrade your weapon as much as you can.
And even after that, it got both me and the NPC down to our last bits of health to take him down.
It's a beatdown that I will definitely keep in mind for the rest of my life as I play the upcoming DLC.
As a melee character I think the best strategy here is to stay away from him unless he gives you a clear opening.
The only other boss I found as annoying as him was Gurranq (first phase). Every other boss even Hoarah Loux and Radagon feel well balanced around melee playstyles.
The beast clergyman has a fair moveset. What he doesn't have is a fair hitbox. His model and posture are so strange that many attacks that should hit don't.