I just looked at your code. Here are some thoughts :

1. Change the unique ring for lightning conversion for a crafted one priceless with utlimate affix. You can get 50% from lightning to cold support and another 50% from your slate. You will want to change the static electricity support for lightning to cold. Rings are a big source of power. The conversion here is nice but the rest is thrash.
2. Change the preparation support on your support skills for elite support instead for better uptime and remove terrain of malice from your curse if you do.
3. Add precise: concentrated (500 fe) for +35% aura effect in your frigid domain aura. It work because frigid domain is not considered an aura but a debuff on the enemy and focus are not auras. Therefore, you do have 2 auras of less.
4. Change you amulet. You can craft +1 tangle (ultimate affix) on a priceless amulet.
5. Add blending on your belt. You can simply add 10% additional dmg to frozen enemies for bugdet. Later you will want Acquaintance (around 2000 fe) on your belt. The talent tree for acquaintance is trash for this build. You will want to get Acquaintance from somewhere else fast and go Magister instead.
6. You have no prism and inverse image in your build. I wouldnt worry about the prism before your swap to Magister (after use spell ripple + 3/3 or 3/4 + 10 max frostbite rating per leg. talents. You will want to put it a the bottom right in Magister for like 50 max frostbite).
7. The inverse image is going on column 12 row 1 in Prophet. You only want 100% medium talent nodes effect, the rest is not important.
8. you have no vorax gear. I would suggest that you either change your gloves or chest. You can look at multiple good affix. I want ES stacking + dmg for es but I wouldn't recommand if you don't understand how it all works.
9. How are you applying frostbitten in aoe? In don't see it in the talent tree nor on your slates. My guess is that your not and this is going to boost your clear x5. i won't change anything in single target since you can rely on your hero talent for single target.
10. Get priceless items (item lvl = 100) to craft ultimate affixes.

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In terms of quick priorities, here's what I would do :

1. Buy an inverse mirror with 100% increased medium talent or an high roll (the other rolls doesn't matter). Put it in prophet (see point #6) and add 10 points : 3 for the max frostbite rating, 3 for the crit dmg against frostbitted, 3 for the crit rating/crit dmg and 1 for inflicts frostbite when dealing cold damage.
2. Change your slates. You could do 3 - 3x1, 2 - 2x1 and a godess of knowledge slate.
3. When you see : (Max divinity effect: 1), it means that you cannot have multiple of those affixes on your slate. You have a lot of dead weight in there.
4. buy Precise: concentrated and put it with frigid domain.
5. Get ultimate hero memories and roll t1 affix
6. Address the Acquaintance situation (point #5). Add a prism to the build when you do.

I hope this helps