I also prefer to run the Cerberus and Golem as a fast/slow threat. How I came to that particular choice of models was by playing some games and finding things I'd like to do better.
My favorite thing to do is use Icy Mirror and December's Curse to lay waste to threats far up the board. Only Nino has more reach. To maintain this strategy, I found the best mix is at least 3 minions with Frozen Heart. If I'm short on stones, I'll take 3 Gamin, but the survivability of the Golem is hard to argue with.
After that, I needed speed to pull off Treasure Hunt and Sabotage, and a model that is good in melee. I combined these requirements in the Cerberus. Leap and Stalk to get up the board and sabotage, and then act as a distraction while I set up multiple December's Curses.
If you're going to be serious about using Icy Mirror agressively, you're going to want an Essence of Power. Going to CA 4 means that you're going to have flips for damage more often than not. While I use lots of soulstones to avoid this, the flip that the Essence provides makes the most out of those blast templates.