Second vote from me for the Ice Mastery on Doms. Sleet and Ice Storm are awesome. Some soft control (knockdown) and good DoT. Never leave home without it for my Mind/Fire. I color the ice powers to look like fire so it fits with my theme and have the shield on min graphics so it doesn't look like I'm a flying glacier.
Also, I would be remiss to not explain that Tough and Weave aren't bad choices. I don't personally see them as a necessity, but for a new Dom player it may be beneficial. Even with all the controls in the world, until you really get used to knowing how to use them all and when to use them all you will pull a lot of aggro.