Man that was a tough fight!!! It took me about 1.5 - 2 hours to figure out how to beat them! Only use Powerful parties!! Im warning you. But there is a way to beat them that works well for me. The only drawback is killing that vampire before he drains any levels
After that I find it to be pretty routine (though as with any battle, the will get you sometimes and you just have to retry). But the way I do it makes it VERY doable(sp?)!
Just thought Id drop a line in case anyone is having trouble with it. Let me know and Ill tell you how I do it. Im sure otherws may have better ways but man was that a tough battle!