Huginn is a must kill. Absolute must kill. As Koz says, he swings the whole game in the wizards favor. Even if you kill him, he has sucked up several actions to do it. Force push is a great way to do that as you slam his annoying self into a wall for 3 unavoidable dice. Perfect strike combined with a melee attack does it too, but is awful late by that point.
I like the Flaming Hellion for the Warlock, very versatile. Firebrand imp is good too. I like the Asyran Cleric for the Priestess. Knight of Westlock or the Royal Archer are great too.