The main thing is you need to deal a lot of damage quickly. If you found the very large ember in New Londo Ruins you can get a weapon to +14 or +15. Once your weapon is up to snuff you have two options: 1) Get close and tank them with Havel's set or something similar (not very rewarding but gets the job done), or 2) Get close and dodge everything. You can roll through all the sword attacks. Get far away for the AOE/grab. As for the slow homing magic-missiles? Well I always just took my lumps and (partially) blocked; could never figure out how to avoid them. With either approach, the main thing is to pick one king, close the distance as quickly as possible, and deal damage quickly while staying on top of him (only dashing away to avoid the AOE/grab).
Edit: Oh, dur. "Help" meant summoning help. I was wondering why you mentioned your level. Never mind me; I always forget that summoning is a thing.