My strategy after the 2.3.2 patch is to have 3 points in imp blizzard, permafrost, and frostbite, and have Icy Veins. Gather up my group of mobs. Get them nice and close together. Frost Nova, run to max blizzard distance, pop Icy Veins, and then lay down the blizzard. I figure with 40% chances to freeze, 75%slow if not and the wave hitting ever 0.8 seconds the mobs should move too much. This is all speculation though.
I should really jump on PTR copy my mage over. Respec frost and see how it works out. It is all theory, who knows how well it will work. I wonder if Ice Floes or any other talent will reduce the cool down on Icy Veins.