If you haven't seen it, check out http://forum.pfsense.org/index.php/topic,56565.msg364122.html#msg364122 for ISO images to install pfSense with Hyper-V support. YMMV.
AFAIK, WSrv12-R2 doesn't include a new version of the Integration Services for BSD -and even if it did, I don't know how you'd go about installing them in a running pfSense install, it likely doesn't have all the required components-, so it is up to the FreeBSD on Hyper-V open source project to release updates. There likely have been improvements in this port (the source patch we're using in the build is over 1 year old). Maybe next month I'll try to see if I can incorporate those fixes in the build process. Meanwhile, you could try the current build to see if it works for you, and post your experiences in that thread.