You can find lists of published patches for Windows Server 2012 Hyper-V & Failover Clustering on the TechNet Wiki:
Credit for the links: Hyper-V.nu
Anyone who is serious about maintaining operational Hyper-V installations should subscribe to the RSS feeds of these two pages and apply the updates. Tools such as System Center Configuration Manager (larger deployments) and Cluster Aware Updating should make this easier.
Consultants, in my opinion, should be maintaining a customised installer of Windows Server 2012 by applying this updates to the install.wim file. This would mean you update the installer every time a new update is released (and verified to be OK – monitor the news feeds). Every new install of WS2012 would be done from this updated installer and be up to date by default.
I did find a script that claims to do it for WIM and VHD files. I’ve not tried it, and I’ve no idea if it will work with VHDX. That would also be a nice solution, especially for boot from VHD, assuming that it works.