Nullify makes BK completely useless. For talents if you know the how good the enemy BK is (from previous matches), BK is the only dmg or your other talents would be useless in the match pick the Direct Current talent to make it harder for BK.
Torvald is a sitting duck. If he's on the point, either rain down sticky bombs, drop grumpy bomb or poppy bomb him away. He has no movement abilities. As long as you have the high ground, he's toasted.