What does the network utilization look like on the machine? on the switch?
This is certainly not normal behavior as video call up should be snappy and responsive. Of course this depends on how the system is configured and the network infrastructure that it is installed on. I suggest that you contact Verint support or provide us an email where we can contact you.
A server can be CPU bound, I/O bound, or network bound. You'll need to minitor all three to track down (or rule out) inadequate resources on the server.
Since you say it's running in a VM you'll need to make sure there are not other VMs on the machine that are stealing resources. If you're not the server hardware administrator you'll need to pull them in as well. Your VM may be reporting low utilization of resources--but that could just be from the perspective of your VM. It could be those hardware resources are being consumed from another VM that your VM doesn't have visibility into.