https://imgur.com/a/nanN5H4 - range showcase
TLDR:
Option A(preferred) - move affix to Major pool, with same weight as +40% damage
Option B - nerf aoe, so that has 50% more radius higher than the one from the Freeze on kill affix".
There are some 'overpowered' things in this game - by overpowered, i mean clearly more powerful than the majority of other items/mutations etc. We know what I'm talking about -things like Baseball Bat or Diverse Deck (Foresight specifically). But all those things, if you think they make your game too easy, you can just ignore and not use them.
But this affix, which occurs only on 'Heavy weapon' tag, is sort of forced on you - it has weight of 80 - over 5 times higher than for example '60% damage vs bleeding targets', and if you get it on a weapon, you very drastically make your life easier in first 3/4 of the game in biomes.
This affix has basically a fullscreen aoe slow - you kill one monster, all monsters on the screen suddenly stop posing any threat to you. It is so much better than any other affix in the pool.
Even if we set aside how good this affix is - having this affix on a weapon makes the gameplay different enough (like different parry times), to justify putting it to major affixes.
What i suggest, is either moving it to major affixes pool, with let's say equal chance to '+40% damage' on items with 'heavy weapon' tag. That way, you get it relatively rarely, but the difference in gameplay while having this affix justifies the rarity.
Alternatively nerf it - reduce the aoe, so that the radius is let's say 50% higher than the one from the affix: 'Victims freeze nearby enemies (1.8 seconds) when they die'.
I prefer the first option,** because my main issue with this affix is how it alters the gameplay, and that's main reason i think it should be more rare.**
The only question is, how playing without this affix on survival weapons will affect balance between melee brutality and melee survival.