Originally Posted by faykan

Well a quick search revealed this post by Roywyn:

Wowhead browsing suggests that the enchant is Black Magic - Spell - World of Warcraft with a 50% chance to proc Black Magic - Spell - World of Warcraft. Probably with a cooldown.

That curse would be not removable, 880 damage on average before buffs/talents. With CoE, FI, partials, and as Arcane or Fire Mage with PWF/ArcInst, that would be 1013 total damage at most.

The 63 Spell Power enchant adds 77 DPS for a Fire Spec of 2 builds ago in Naxx-10 gear.
That means over 15 seconds, the full Black Ice duration, it would add 1155 damage.

So, um, yay? Even if the enchant proc had no cooldown and reprocs didn't reset the tick timer (like on Deadly Poison or Affliction/Shadow talents) and the proc was always up, the spell power enchant would be better.
It would however be useful when AoEing to curse all mobs you hit. If all the extremely favourable conditions above were true, something I don't believe.