Gameplay tactics on the large map.

Yes, with this talent, any unit with a cold spell will be very effective.

Yesterday, I played with a friend in a strategy game; he played as Deleb, and I played as Nur. Right from the start, he got the "Secret Defensive Cloak" (an item that provides resistance to water and ice) - as a result, the "Deadly Cold" spell dealt 1005 damage (to the ballista's health) instead of 1100. This was one of the factors that led to our defeat.

So, fellow Warlocks, keep in mind that items that provide resistance to ice don't prevent a unit from being destroyed by a spell (maybe this is common knowledge, but it was a revelation for me, and it might be useful to someone).