For me Ice Sweep isnt doing anything it goes right through enemies not effecting them. Happened with Fallen Sky weapon not sure about others with this rune.
I assume it work as Plague Sweep on Gnarled Harpoon you can buy form wood vendor, it don’t hit enemies very close to you(think expending spear at max range and only blade of spear cause damage around you.) , but I found Plague Sweep very useful as it cost only 25 focus and hit very hard around you and and it got good range…