Then they should change the way Ice blades work or won't be a viable class. Right now this spell fail a lot, you need to use it like 3-4 times before all mobs have the debuff on them.
If you fix this bug you also need to do these changes:
1 - Remove that 5% mana cost. Right now using only in BIG pulls I need 30 mana potions E type per run. Using this skill with small group of mobs so all have a debuff, imagine how many mana pots 
2 - GCD. If play style change and we need to use it more often to apply the debuff, that global cd needs to be removed.
3 - Type of aoe. A stright line aoe has always problems. I propose to change it like m/d aoe or same type as you did with warden so all mobs get the debuff on them with just 1 skill not with 3-4 cose of terrain.
4 - Also have to consider these kind of debuffs have 1 second delay. Skill have 3s cd so many times you will use on a mob and it won't do aoe cose rest didn't get their debuff yet.
Easier than all this, remove that condition from the skill. Class was already weak with this bug, why change it now.
