Dark/Ice is stronger statistically. You get huge -Damage debuffs on top of the -ToHit, and better controls.
However, in actual gameplay, Dark/Ice is vulnerable to spread-out spawns, to spawns that are hard to keep in place, and to adds. Time/Ice is less vulnerable since in general the mobs will come to you and thus get debuffed, and their positioning doesn't matter with the greater +Defense.
So, basically, Dark/Ice has more upside but is more vulnerable to spikes of vulnerability, while Time/Ice is a bit weaker at the top end but has less to worry about with regards to mob placement.
Dark is a lot stronger against AVs, if you care to solo those. Otherwise, Time is probably stronger... because a well-built character doesn't generally have worries when the fight is going as planned... it when chaos happens that trouble may occur. And Time's defensive abilities are less vulnerable to chaos.