"You really used vmxnet3 for the ESXi VMs ???"
Well, I found out the hard way.....lol 
"100 - 120 Mb/s ?"
Yup, MB/s. That was file copy. That's exactly what I did for my iscsi test. Connected the esxi VM's to the host only vmnet1 and pointed the local iscsi target to present to that IP subnet and bingo!