Rather than just review Witch Hunt, GameZone has taken the time to offer up their impressions of every downloadable addon for Dragon Age: Origins (save for Awakening) in a single editorial called "The Conclusion of the Dragon Age: Origins Saga". Since Witch Hunt is the most relevant, though, I'll quote from their take on that:
If you upload your character who has played through Awakening and/or Golems of Amgarrak, then the ending of Witch Hunt will definitely not make sense since there is a bug that has Morrigan forgetting your special night together. Instead, the bug revolves around as if you refused the Dark Ritual even if you or Alistair did not refuse. There are reported to be other continuity issues in relation to the previous DLC, so it's definitely a head scratcher on what happened with bug testing.
It's safe to say my relationship with Dragon Age: Origins didn't end on a good note. While it's a farewell to Dragon Age, it's an awkward one at that. I was hoping to tie up some loose ends, or at least to have questions answered, but unfortunately, the bugs dampened the overall experience. On top of that, the ending is even more ambiguous than it should have been.