Snowblind adds invaluable Chill to the build when we don't have it and extra Blind. To slam PrefixAttunement onto one you can use an exalted helm from any class and won't make the slam class-specific.
We are using Frozen Ire over a dagger as it caps our SuffixNecrotic Resistance so we can get SuffixCold Resistance elsewhere, gives 658% SuffixFreeze Rate Multiplier where daggers can't get that, there are no good cold dagger uniques to slam, gives higher Frostbite base damage (even a 0 LP Frozen Ire will give you higher vs a quad damage rolled Crystal Wand such as Crystal Wand I found, a dagger way less so we trade less stacks for way more damage), frees up the poison nodes you'd take for defensive nodes like Shroud of Dusk to stay alive in high corruption and the 120% PrefixCold Damage and Tundra Nova for extra ward generation are nice freebies.
Snowdrift is our second source of cold penetration stack with Knowledge of Immunity so we want as much SuffixFreeze Rate Multiplier as possible. However PrefixDamage Over Time scales the base damage of Frostbite harder than SuffixFreeze Rate Multiplier so that is the first priority. SuffixFreeze Rate Multiplier scales the base damage of Frostbite harder than PrefixCold Damage. You should always have a T7 PrefixElemental Damage Over Time roll wherever possible as this will scale Frostbite the hardest.
Ucenui's Sphere requires your PrefixAttunement to equal your PrefixIntelligence in order to give you the triple cold damage buff which will cause Frostbite base damage to ramp up massively vs bosses. It is 100% worth adjusting for and we'll use one of our Snowblind prefixes to do so.
Double Heirloom of the Last Nomad is purely for the double SuffixCold Resistance, high SuffixHealth and to cap your SuffixVoid Resistance so we can stack SuffixCold Resistance elsewhere. Remember, Knowledge of Immunity converts every 5% uncapped SuffixCold Resistance to 3% cold penetration for Acid Flask. It's worth noting here that there is no penetration cap. Penetration bypasses a given amount of enemy % res. This even can go into the negative, so even on enemies with 0 res (which most enemies have) it will increase your daage. Frostbite is affected by damage modifiers from the skill tree and attribute scaling of the skill that applies it so 100% will be impacted by your SuffixCold Resistance. A more expensive alternative is double Red Ring of Atlaria. We won’t be using it as it’s unrealistic you will ever find or buy one in 3+ LP in a cycle.
Xithara's Conundrum prevents SuffixHealth Regeneration giving us more stable ward. Additionally it grants us burst ward when we consume a potion, preventing our potions from stopping ward generation due to the life drain effect of Exsanguinous and PrefixExperimental Ward per Missing Health. The leech won’t be an issue as we aren’t leeching anyways. A more expensive, tankier alternative is Orian's Eye. We won’t be using it as it’s unrealistic you will ever find or buy one in 3+ LP in a cycle.
The Spidersilk Sash belt offers a huge boost in cold resistance. You can double rolls in the implicit and 2 suffixes giving up to 92% which is a tonne of cold penetration and ward retention. We be using it to cap our SuffixPhysical Resistance.
You want at least T5 PrefixExperimental Mana on Potion Use on the belt for mana sustain in longer fights vs bosses and orobyss and T6 PrefixExperimental Frenzy Effect on the boots for an insane attack speed buff after every Aerial Assault. Too much attack speed is never an issue with this build as we want to get out as much Frostbite DoT out in any given window of opportunity.
In order of priority from most to least important: PrefixElemental Damage Over Time > PrefixDamage Over Time > SuffixCold Resistance > SuffixFreeze Rate Multiplier > PrefixCold Damage.
Legendary potential priority order on gear is listed below from most important (top) to least important (bottom).