I was going to mention the same one curse did, sort of a shockwave themed suffix or prefix. Bastard mind hacker.

So some of my other ideas are maybe less tenable...
A hit dealing over X% of enemies maximum Health total adds
bleed status which drains enemies health based on X% of their maximum health over X number of seconds. I know there was something like bleed in d2, but basically I think bleed/wounds needed to be more... interesting. In d2 it didn't do
s**** in nightmare and hell. What? Do enemies just stop caring that they're
bleeding to death? In the way presented here it's balanced because it's initiated only by a large enough chunk of their health being removed by a single hit rather than by any weak old hit. This is more or less something that should be innately imbedded in all 'sharp' weapons and abilities.
% of damage damages enemies mana or stamina (assuming they use mana and st in this one rather than just leaving those infinite, no clue). "of the wraith", "of exhaustion".
Attack has % chance of disabling a random enemy skill for x number of seconds (assuming enemies have a larger index of s**** to use, would be nice for pvp though). "of forgetfulness". Aww... that sounds kind of sweet. Grandpa forgot how to use his fireball.
Damage dealt to you that deals over x% of maximum health have a chance to cause you to become berserk (more physical damage, can't use magic spells but still certain mana based skills).
Attack adds burn/immolation over x seconds. (burn based on % of original damage, lowering incrementally over the duration). It would be awesome to see enemies on fire. : )