G'day, I am seeing the same issue with vSphere 6.0u1 using multiple VCs using linked mode via multiple PSC and single SSO domain. I get varying results using the web client and different browsers. However the issue of disappearing hosts from the the host view remains. Likewise the host view is stable using the "fat" client.
I would be interested to know if you find a fix for this?
Cheers
J