I agree about the musicians. It sounds like you have a nice basis for an army! The main thing I'd want to think about is how you plan to win combats... it'd be nice if you had more of a rock-hard unit in there that could hold your opponent while you gain the flank and negate his ranks, and win through superior
CR. A screaming bell could be very nice for this.
You have the numbers for rats, but I think you just need to flesh out what your strategy will be a little more... there's a lot of skaven lists up that you could browse through for ideas