The ice mage is an amazing class to play if you want damage and crowd control to support your team, or to simply keep all of your enemies at bay at all times. I like the Frostweaver more than the Pyromancer, because it can constantly keep the enemies frozen, so in very demanding situations you can easily get out by simply taking advantage of the frozen enemies.

It is also very good when dealing with enemies that apply crowd control, because it doesn't need a support to remove negative effects off them, because they can simply use the Enhanced Blink for that.

Skills:

Ice Ward: Summons an ice ward which deals great damage to up to 6 targets and freezes them for some time.
Enhanced Blink: Dashes forward in a gust of howling wind, dealing damage to nearby enemies and freezing them, while also removing all crowd control debuffs and healing the caster.
Ice Storm: Summon a blizzard for a period of time which deals damage and slows the enemies continuously in the given area. It also has a chance to freeze the enemies.

As you can see, the Frostweaver is a very crowd control focused class, mostly because it can have the enemies frozen most of the time. It is amazing for multiplayer dungeons, especially if you can use the Enhanced Blink to get yourself to safety and heal (and remove crowd control if you have any applied).