Ice Nova of Deep Freeze

So ive been running in game boss timing dps tests and weirdly Ice Nova of Deep Freeze performs much better then regular Ice Nova, while it should have significantly less damage. POB states a damage drop of 36%. But in the timing tests I have around 30% more damage on average. How is this possible?

And no i dont have mods that give me more damage on forzen targets. Also the boss was perma frozen with both skills in both scenarios.