We downed him on both 25m and 10m last night and it is a fairly fun fight. I got his ENTIRE hitbox on the ice and he still burrowed so it is definitive that you cannot prevent phase 2 on live.
What worked best for us was similar to the vid keeping all our melee on the boss non-stop and just have ranged switch to burn down ads as needed and also dropping as much frost as possible.
I worry about fights like faction champions and this on heroic diff but it is fairly straight forward on normal (although 25m is definitely much more taxing then 10man).
One thing to be aware of, I tend to pickup ads without thinking and it is not a good idea to have the MT have like 10 stacks of the ad debuffs lol

