The trick SEEMS to be killing them quickly, at least the first two or else you get overwhelmed by the others firing off the seeker blasts and dashing in to get personal with you as well. The Crest shield and Havel Armor are actually working pretty well since they provide huge resistance and rolling really isn't an issue with them...just not killing them fast enough.
I'll post what I did to FINALLY beat these guys and get into the Covenant I'd wanted since I started.
Makes sure you buy the Iron Skin from the Pyromancer in the Firelink, it makes it a ton easier.
I had a Lightning Uchi+3 when attempting this. My rings were the Abyss Ring and Steel Protection. My est flasks were also +3.
Start off, I barreled through New Londo and to the Abyss, ran down the stairs(Don't jump off) and when I hit end, I switched to my strongest Armor(Iron). I then hopped in, having my Uchi and Pyrocatalyst equipped. Once the first king spawned and began approaching, I used my first cast. I then tanked his hits like a boss while two handing the Uchi. Slayed the first before it ran out, so I just stayed away a little until it did. Casted it again, killed the second. Repeated for third. I switched back to my shield and did as much as I could in my last iron skin. From there I was careful, kept my shield up and walked in a counterclockwise circle while striking after he did. After a little bit of time, the sucker went down and the four hours I spent on them was finally worth it.