Just for fun, I'm going to throw down some odds for some of Top Cow's other artifact bearers:
Finnagen/Glacier Stone:
1) Nightwing - 9-10/10 like the others
2) Spider-man 6.5/10. Not quite as good as Witchblade, he could get webbed up and miss with his ice, but he's one of the toughest bearers and strong and can make enough ice that it's hard to avoid.
3) Flash- Near-Zero. Sure, icing the ground could make things slippery for Flash, but Flash is kinda used to that.
4) Magneto - 0/10
5) Wonder Woman- 0/10
6) Martian Manhunter- 0/10
7) Thor 0/10
8) Rachel Summers (Phoenix) 0/10
9) Doctor Fate 0/10
Sabine with the Wheel of Shadows:
1) Nightwing- As usual, 10/10
2) Spider-man- Not as much range as the others, but her time powers are very dangerous and likewise her slip-between-seconds pseudo teleport could catch him off guard. 8/10
3) Flash- Oh, this is something of a tough one. He might be able to take her out, but if he runs into her time-sapping cloud by mistake, or gets caught off guard by a time-teleport.... 110.
4) Magneto- He still probably takes her from a distance, but hit him with the time powers and it's over. She's the second best artifact bearer to take him on, behind the Darkness. 2/10.
5) Wonder Woman- Hah, let us age the immortal! Who's too powerful mystically to age anyway. 0/10
6) Martian Manhunter- While technically mortal, very long lifespan, and all kinds of other advantages, 0/10.
7) Thor- See Wonder Woman. 0/10
8) Rachel Summers (Phoenix). Time is no defense against psychics. 0.5/10
9) Doctor Fate. Mortal, but can resist the effects 0/10
Probably the most dangerous artifact bearer in a one-on-one fight against non-mystic foes.