We are seeing the same issue. Before with ESXi 5.1 and View 5.2, if a VM got stuck, I would go into the server console and kill the VM with esxtop. Then I'd go in View and do remove desktop.
Ever since the upgrade to ESXi 5.5 (we ran View 5.2 with ESXi 5.5 for a few months) we've experience this problem. Still having the issue now with View 5.3 The VM can no longer be killed with esxtop. And like you, only a host reboot will do it. And yes our servers hang as well on shutdown. We power cycle once we see the host disconnect from vCenter.
I've opened a case with VMWare this morning. Hopefully they can solve this issue.
One question for you: Are you running a GRID card by nVidia (K1 or K2) and/or a Teradici APEX 2800 card in you servers?
Thanks!
Luc