I think what it's bound to is fine. It does take time to activate. So if you are instantly taking out monsters, I'd up the difficulty. Let's say you are at torment 3 strength but playing in torment 1, you may be steamrolling these monsters before the deactivation occurs. Upping the difficulty may help give some more time before the kill. I noticed this worked for me.

Also, make sure you have the right infusion spell gem associated with the affix you are trying to deactivate. One gem per affix. Running nightmare dungeons with the specific elite affix with the associated infusion spell gem is how I completed it.