I've rolled about half of the all possible controller combinations and my ice/storm is still my favorite.
You are right that the AoE immobilizes cancel some of the goodness of ice slick but I don't look at it that way. I see that "lack of synergy" as a way to vary my strategy from mob to mob. It keeps the game very interesting.
She's lvl 45 now and I started her long before AE so I played through a lot of scenarios. In the early days (pre 30) ice slick and freezing rain were a great combo.
In a lot of the AE mishes, the pace is a lot faster. Sometimes I'll use a combination of Frostbite, Freezing Rain, Lightening Storm and hurricane to keep everyone bunched. Other times I may go retro and use the ice slick, freezing rain, hurricane combo.
The thing about ice slick is that it still works for enemies you may miss with your AoE imm/holds. After a while, your accuracy will be pretty high and your holds will work better but it's always good to have an ice slick underneath for those missed.
My recharges are fast enough where I can throw an ice slick, circle around to fire off a lightening storm, return to the other side and get another LS up before the ice is gone.
Ice/Storm gives you so many possibilities. It's not so much a lack of synergy, it's versatility of abilities. I love it!
