HI Snamidro,
Today we got the confirmation from customer that there was some vlan issue in his network to which servers were connected and after untagging the vlan now no retransmission.
I even replicated the setup in my lab, with 3 Dell servers which had BCM5720 and Intel i350 and connected to a plain 1G switch and i didnt notice a single retransmission.
I even updated the NIC driver on customers setup, network firmware still same issue.
My next POA to customer was to bypass his Core Switch and connect a plain switch between the servers. So finally it came out to be configuration issue.
But vmware has to think about a proper solution, as customer claims no issues with ESXi 6 but only issue when they updated to ESXI 6.5
I hope my POA would help you.