It is definitely viable, but kind of struggles right now. However if you want to use her i supppose you do it in an offensive Hail team. Either use a SubDisable set with Blizzard and Tbolt, to force many switches so that residual damage build up, along with your own decently powerful hits, or use him with a Spikes set. But definitely use him in a hail team, otherwise it pretty much sucks.

Is Froslass usable in OU? I do love it so!