I have tried Necropetence, on my MagBlade and my conclusion is that it's not all that good a choice. Reason, you can't pop your shades unless you are in range of an enemy, so you don't get the Max Magic Boost from the set until you get the shades, but your magic will not regen up to the new level before combat is typically engaged.
Yes, you get the DPS benefit from the higher magic, but to me without the corresponding pool increase, it is not an ideal situation.