All you need to kill the ones at untended Graves is a dark sword+10, enchanted with dark magic. You can use the ring that removes footstep sounds and/or sneak up on them from behind, since you can attack all of them from behind if timing and the direction you're coming from is right. give em a little backstab, reduce them to half hp. Just when they try to get up again, charge a heavy attack (all twohanded ofc) and kill them. Still works in Ng+4 for me. I had 52 strength, 47 dex, 35 int and 37 faith when I first tried it on Ng+4. If this combos dmg is not high enough for you to 2-shot them yet, pick up and equip the hornet ring that conviently lies a little hidden in the same area, equip it and get higher backstab dmg from it. Then it should be enough.