If you want to run your own dns, you could just install the unbound package on pfsense - no need for MS dns, which I don't believe is viable on WHS anyway.. They really striped out the actual useful features of server with WHS, like dns.. Now maybe there is some patch or something to turn it back on?
Or you could always just run bind on any box on your network, even your WHS, etc.
But if you want to run your own dns, I would really check out unbound package. Its be working great on my setup. Has dnssec support and ipv6 support as well. And has been pretty much rock solid, I keep hearing that it will be fully integrated into the 2.1 line vs a package which I am very much in favor of!
Only thing that would be nicer would be to create package or easy howto in running full blown bind on pfsense.