Take a casket! If you can protect it well, in such a low level game it will wreak havoc! Your opponent will have 3 dispell dice, so either he has to use them all on the casket every turn and you pretty much get all your spells without fear, or he has to waste a DD every turn. Such an elite army as that would be crushed by the casket fairly easily. The only realy problem would be if the opponent is Khorne or Tzeentch in which case you'd be in trouble no matter how you looked at it, though then he wouldn't be able to have the lvl 2 wizard. I'd probably also take a unit of tomb guard and another tomb scorp. All those chaos models have at least a 5+ save, so the killing blow will be fairly usefull, and so will the high S and T. (probably also split the large bow unit into 2 units or cut it down to 10 and use the points for something else.)