More info on O&S, with Smough taken down first:
As previously mentioned, try to keep both of them on screen at once so that you know when attacks are coming at all times. If you can, keep Smough between you and Ornstein, because Smough's bulk actually stops some of Ornstein's spear charges. Smough goes down quickly with the lightning spear so just swap to 2 hand during his recovery and stab him when you can. He should go down in 3 or so reps of this. Make sure you roll in the right direction against his hammer attacks, because sometimes they catch one type of roll or another.
For Super Ornstein, I used the same ranged tactic that was mentioned, except replace soul arrows with poison/regular arrows. Super Ornstein can be poisoned, and if you space him properly behind broken pillars, he'll try to lightning bolt you repeatedly when the bolts actually fizzle on a pillar in front of you, while still letting you shoot arrows at him. It's lame, but so is two FUCKING CRAZY BOSS DUDES ganging up on you, so I didn't feel bad about it.