I used a +5 silver knight spear and that seemed to do pretty well against him on NG+. Though on a faith-based build with access to sunlight blade you probably want to stick with enchantable weapons. And low STR/DEX means you want to use weapons with high base damage, since you're not going to be getting much from stat scaling. A +14/+15 gargoyle halberd would be great if you happen to have one. Pop SB on that one with PW going (or even without PW - I never use it, myself) and you'll swing for the fences.
Also, with that VIT and END you should really consider committing to the ring of faith and protection. The bonus to HP and Stamina is well worth it.