Cool down is really short, and it hits like a truck when locked on. It could be interrupted as any spell could but its on a short cool down. Play around and see what you like.
The thing about frost mage t1 is that all the other options are garbage. Even if all you do with ray is soak an interrupt 80% of the times you cast it, it's still better than the other talents.
RoF is the only viable option. It's stupid broken but there's nothing else. The next best would be Lonely Winter but the buff barely covers the lack of water elemental.