I've read that this ability can be avoided, but I'm unable to do so.
Can others share their experiences with this? I'm constantly moving
once targeted, but always get hit. Is it simply a matter of watching
when Rimefang attacks (I've tried this, but I may just not be quick
enough)?
Any advice would be appreciated.
I think you can't avoid it. You have to move if you are near other players,
because they can be hit by the hoarfrost if they are too close.