Well, their powers are of a different sort, so it's somewhat hard to compare. Physically they're noticeably less strong, though they often can make many constructs and the like, the Darkness especially (but on the flip side, the Darknesses' constructs are also easily destroyed).
One problem is going to be that neither the Witchblade nor Angelus's energy attacks, some of their best offense, are going to do much good against Carol, and I would think energy blasts will count as 'bright light' to the Darknesses's constructs.
Definitely a much better fight than Surfer though.
Is this a new development? Classic Darkness and Witchblade are no-where near herald level, and iirc the biggest feat of destruction any of them has done is Jackie sinking a naval task force (which was far beyond anything he had done prior to that when he did it).