Hibernate will help you remain upstanding when normally you'd hit the deck.
Frozen aura is a teeny pbaoe sleep useful for keeping an additional or current bulk of the group at bay unless someone in their wisdom wakes them and if your not careful quite often your own aura will. Im a fan of mass sleeps so i would have this if it was a much larger pbaoe. Detoggles all unprotected for sleep enemies. Most would say dont bother with it.
Build up helps with acc versus -tohit and buffs damage which then stacks with gauntlet and then hopefully very good with something like ice storm.
He will honor his words; he will definitely carry out his actions. What he promises he will fulfill. He does not care about his bodily self, putting his life and death aside to come forward for another's troubled besiegement. He does not boast about his ability, or shamelessly extol his own virtues. - Sima Qian.
As Shannon says, Hibernate is a great power that can be instantly smashed on when you think you are in trouble or you just need to replenish some endurance near the end of a fight - it is up pretty fast with 3 recharges. As an ice/ice you will basically be made entirely of aggro, but throwing out a taunt before you hibernate ensures further safety for your team as the enemies flap about on your ice patch and continue to hate you with a 2-taunt-enhancers chilling embrace. Yummy.
I chose not to take frozen aura as later on in the game AOEs are rife thanks to ice's unbeatable aggro management, and if you are running icicles the critters will immediately wake up anyway. It is easily one of the worst final tier powers for a tanker melee set purely as it has such little practical application. However, there may be one or two people out there who like it so good luck to them.
Build-up: I took this in my mid-30s to help make sure that my holds and debuffs hit bigger beasties. Even though Ice Melee does pretty laughable damage, BU really helps you keep tightly packed mobs under control with Frost, and the damage soon adds up with Icicles. You can also execute a Paragon Protector with Greater Ice Sword just before he/she pops MoG/Elude/Stoppable.
If you would like me to post my icy slag's build, let me know - but at the end of the day, remember this: purple pills are your friend 
Oh and fortitude or bubbles don't go amiss either ;D
Pookie!!!
I dont know why they cant make frozen aura do pbaoe "fear" like with dark armour but call it "shiver" and leave off the scarey graphics. oh wait i do, itll make the /icetank too good? or would it when you have icepatch anyways? Icepatch wont do for flyers, the pbaoe fear maybe could.
He will honor his words; he will definitely carry out his actions. What he promises he will fulfill. He does not care about his bodily self, putting his life and death aside to come forward for another's troubled besiegement. He does not boast about his ability, or shamelessly extol his own virtues. - Sima Qian.
How important is hibernate and frozen aura? (making my first tank ice/ice).
PS: should i bother with build up?