That seems very strange, unicast traffic should never be visible to other VMs like that. Are you sure promiscuous mode is disabled on the vSwitch AND port group level and one doesn't override the other?
Also post the output of the following commands from the host:
# esxcli network vswitch standard policy security get -v [vSwitchName]
# esxcli network vswitch standard portgroup policy security get -p [PortGroupName]
When ESXi rejects promiscuous mode on a port it also logs this to the vmkernel log file. Check your vmkernel logs if there are any messages similar to this one:
2013-05-25T12:52:58.596+02:00 vmkernel cpu3:7201556)etherswitch: L2Sec_EnforcePortCompliance:226: client VM-NAME.eth1 requested promiscuous mode on port 0x5000153, disallowed by vswitch policy
Also take a look at the vmware.log file in the VM's directory.