I can't give you an exact build as I changed it around a lot.
But in general:
Always 11 points in Sorcery to maximize DPS.
9 points in Witchcraft so you can get Baleful Recharge. With this you will never be out of mana.
You can put the last 3 points in Songcraft for Hummingbird Ditty and the 2 CC.
You can't get the 5% cast speed reduction from Songcraft unless you drop important things form Witchcraft or Sorcery.
*I made a big EDIT because I had forgot about Baleful Recharge in my original reply.