Earlier on here I was asking what enchant would be goo for a tanking weapon and the consensus u got was it really doesn't matter that much, they all have their uses. So i tried out several including Berserk, Armsman, Mighty Spell-power, and Black Magic. To my surprise, Black magic gave me and almost uncomfortable boost in threat. I went to an ICC 10man and was off-tanking with a warrior. The warrior had far better gear than i did as I have adjust reached ICC lvl and hes been here a while. Throughout every fight I was inadvertently pulling off him all the time. On fights with taunting at stacks my only difficulty was trying to stay UNDER his threat. And I was doing almost double his damage. I have tanked with him a few times before. He is not a bad tank by any means, so its not like he just didn't know how to build threat. And I have never had that problem working with him before.
Therefor I suggest maybe a few of you could try out Black Magic and see what happens, get a better idea of the effect outside my one tank experience.