I think this happens only on vCenter servers with extra agent installed.
Is your vsphere special agent configured like it was in the old versions (vSphere host + agent)?
I would try to use the configuration the newer way that i setup the normal agent and the vsphere special agent as normal datasource.
In every agent the system time is the last output to prevent the problem you described.
In this old setting i think you get first the agent output generated and then it fetches the special agent output and there comes the delay.