Essentially you are going with a cheese army that was discussed at length in another thread. I would mix it up a bit. Maybe one of those units of horrors for Plaguebeaers.
Maybe swap out one unit of flamers for some bloodcrushers.
As it stands your army tactic is to magic missle, repeat, repeat, repeat, repeat, repeat, then shooty of 5d6, 6d6 with the hero in it.
Second verse same as the first.
Pray you dont miscast.