Seems to be a pretty good legendary.
Especially in encounters where you have timed AoE-Phases.
A good example would be Odyn, Helya, Eye or Renferal.
The 3sec-Stun is a nice augmentation.
Its probably second best on ST.
Bracers + Cold Core, that's going to be some crazy damage spikes.
Item:
http://ptr.wowhead.com/item=144293/consorts-cold-core
I do not have a single frost Legendary yet, but if I could chose than I would pick this one
Its awesome for M+ and most of the current raid encounters.