To be fair it's not useless for pve/pvp. But in current maps enemies seem to die too fast vs procs for the hailstone freeze to actually matter, while in pvp all classes have a way to avoid cc and enough haste to keep it up for most of the fight.
I 100% agree tho, that a small effect would be nice to make this gem a bit more special.
Then again the first gem with proc, cursed skull, also had no effect and also had underwhelming stats and proc/proc chance.