I usually get it after sotm and it rocks! you melt anyone since your ult with staff does massive magic damage and your toxic gas already does huge damage. Try it, its really and no you do not take extra damage
I forget the exact math but spell shards are retarded. It's like 4575 for a 12%? Increase in dmg vs shamans. When Hellflower is barely more and silences and does more dmg. Also the spell cd reduction is already bad but on dev it's useless.