This seems to be as of the Yesterdays beta. When I use Rain of Ice, it seems to have no area effect damage. I'll cast in on a bunch of creeps and I'll only see one damage number pop up. To make sure it just wasn't a glitch with the floating combat numbers, I made sure to highlight the healthbars and it indead didn't do any damage to other creeps.
That same match there was another bug where one of the Demigods got totally frozen and he became untargetable by the other players.
