Search and read before posting. A simple forum search for "Black Magic" turns up the answer within the first 5 posts, even assuming you don't trust the FAQ to be correct.
I've been doing my best to keep up with the 4.0 discussions in the multiple threads here, and I recently noticed that Aldriana posted that Mongoose is the ideal weapon enchant in his 4.0.1 Rogue FAQ thread. However, I'm curious is if this is true for both the MH and the OH or just the MH as I saw previously. I was under the impression that Black Magic was best for OH, so I hope to get this cleared up.