Here's an update
I logged into a Windows 8.1 Linked Clone when it was stuck at the domain join stage. I removed it from the domain and within a few seconds, the VM reboots and View Composer/Connection manager successfully joins it to the domain. So I thought, that's odd it seems to get stuck when removing the machine from the domain before adding it. So I created a new snapshot with the VM NOT JOINED to the domain. After a recompose the VM builds and joins to the domain successfully. Even though this goes against all documentation....
I thought, maybe its a vSphere compatibility issue. So I updated vcenter and vpshere to 5.5, then updated the VMware tools on the VM and reinstalled the view agent. Same problem.
For some reason when the master is joined to the domain it fails with "Domain join failedError 2 (0x2): The system cannot find the file specified." However if the master is in a workgroup, all is well.
Has anyone built a linked clone pool with Windows 8.1 yet?