Nov 2nd 2008 6:48AM Earlier today I used Thunderstorm on stunned mobs and they _didn't_ knock back.
So.. I'm guessing with Improved Fire Nova, the two second stun will give the shaman the chance to use Thunderstorm without having a knockback. I'll have to check this out some more.. but it seems like it should work. The only problem would be if the stun didn't go through.